Apparent CMU CL compiler bug

I apologize for the vague subject line; I'm not familiar enough
with the compiler's internals to isolate one line's worth of
useful information.

I've been playing with evolutionary programming, which is a
great source of somewhat random code to feed to the compiler.
If this is indeed a compiler bug, then it's the second I've
found in this way! Here, first of all, are some details of
my system.

Hardware: ia32 (Athlon)
OS:       FreeBSD 4.something
CMU CL:   version 18d, compiled using FreeBSD port

This machine has never, so far as I know, suffered anything
that looked much like hardware trouble, which is why I'm
tentatively choosing to blame CMU CL rather than the hardware.

Here's what I believe to be the relevant portion of the
backtrace. (After that it goes into my own code.)

Type-error in KERNEL::OBJECT-NOT-TYPE-ERROR-HANDLER:
   536870911 is not of type (MOD 536870911)

Restarts:
  0: [ABORT] Return to Top-Level.

Debug  (type H for help)

(C::VOLATILE-INFO-LOOKUP 3
                         #<C::VOLATILE-INFO-ENV "Working">
                         #:INDEX-0
                         536870911)[:EXTERNAL]
Source: Error finding source: 
Error in function DEBUG::GET-FILE-TOP-LEVEL-FORM:  Source file no longer exists:
  target:compiler/globaldb.lisp.
0] backtrace
0: (C::VOLATILE-INFO-LOOKUP 3
                            #<C::VOLATILE-INFO-ENV "Working">
                            #:INDEX-0
                            536870911)[:EXTERNAL]
1: (C::LOOKUP-IGNORING-GLOBAL-CACHE
    (#<C::VOLATILE-INFO-ENV "Working"> #<C::COMPACT-INFO-ENV "Auxiliary">
     #<C::COMPACT-INFO-ENV "X86 backend"> #<C::COMPACT-INFO-ENV "Compiler">
     #<C::COMPACT-INFO-ENV "Kernel">))
2: (C::GET-INFO-VALUE #:INDEX-0 14 NIL)
3: (C::GET-INFO-VALUE 2 #:INDEX-0 14 301989455)[:EXTERNAL]
4: (C::VARIFY-LAMBDA-ARG #:INDEX-0 (ARRAY))
5: (C::IR1-CONVERT-LAMBDA
    (LAMBDA (ARRAY #:INDEX-0)
      (LET* #
        #))
    NIL
    NIL)
6: (C::IR1-CONVERT-INLINE-LAMBDA
    (LAMBDA (ARRAY #:INDEX-0)
      (LET* #
        #))
    NIL
    NIL)
7: (C::TRANSFORM-CALL
    #<C::COMBINATION #x48C91F45
        FUN= #<C::REF #x48C91F15  LEAF= #<C::GLOBAL-VAR 48C8315D>>
        ARGS= (#<C::REF 48C91FBD> #<C::REF 48CC6045>)>
    (LAMBDA (ARRAY #:INDEX-0)
      (LET* #
        #)))
8: (C::IR1-OPTIMIZE-COMBINATION
    #<C::COMBINATION #x48C91F45
        FUN= #<C::REF #x48C91F15  LEAF= #<C::GLOBAL-VAR 48C8315D>>
        ARGS= (#<C::REF 48C91FBD> #<C::REF 48CC6045>)>)
9: (C::IR1-OPTIMIZE
    #<C:COMPONENT #x48CCBF1D  NAME= "LAMBDA (COUPLINGS)"  REANALYZE= T>)
10: (C::IR1-OPTIMIZE-UNTIL-DONE
     #<C:COMPONENT #x48CCBF1D  NAME= "LAMBDA (COUPLINGS)"  REANALYZE= T>)
11: (C::IR1-PHASES
     #<C:COMPONENT #x48CCBF1D  NAME= "LAMBDA (COUPLINGS)"  REANALYZE= T>)
12: (C::COMPILE-COMPONENT
     #<C:COMPONENT #x48CCBF1D  NAME= "LAMBDA (COUPLINGS)"  REANALYZE= T>)
13: (#:G0)
14: (COMPILE NIL
             (LAMBDA (COUPLINGS)
               (DECLARE # # # #)
               (* -0.28157314694834445d0 # #)))
15: (COMPILE 2
             NIL
             (LAMBDA (COUPLINGS)
               (DECLARE # # # #)
               (* -0.28157314694834445d0 # #)))[:EXTERNAL]

And, since the forms hidden by those hashes are potentially
relevant:

15] pp
(COMPILE 2
             NIL
             (LAMBDA (COUPLINGS)
               (DECLARE (IGNORABLE COUPLINGS)
                        (TYPE (ARRAY DOUBLE-FLOAT (3)) COUPLINGS)
                        (VALUES DOUBLE-FLOAT)
                        (OPTIMIZE (INHIBIT-WARNINGS 3)))
               (* -0.28157314694834445d0
                  (+ (AREF COUPLINGS 1)
                     (* (AREF COUPLINGS 0)
                        1.6423813483707832d0
                        -0.28157314694834445d0
                        (+ (AREF COUPLINGS 0)
                           (* 1.6423813483707832d0 (AREF COUPLINGS 1))
                           (* (AREF COUPLINGS 0)
                              -3.970822355081399d0
                              -3.970822355081399d0))
                        -0.28157314694834445d0
                        (+
                         (* (AREF COUPLINGS 2)
                            -4.2575969041029795d0
                            (SQUARE
                             (* (AREF COUPLINGS 2)
                                (+ (AREF COUPLINGS 0)
                                   (AREF COUPLINGS 1)
                                   (AREF COUPLINGS 0))))
                            (AREF COUPLINGS 2)
                            (AREF COUPLINGS 1))
                         (AREF COUPLINGS 1)
                         -0.01036753259739509d0
                         (AREF COUPLINGS 1))
                        (AREF COUPLINGS 2))
                     (ATAN (AREF COUPLINGS 1)
                           (*
                            (+
                             (* 3.5783156939259086d0
                                (+
                                 (* 1.9322815947063288d0
                                    3.5783156939259086d0
                                    (AREF COUPLINGS 0))
                                 (AREF COUPLINGS 0)
                                 (AREF COUPLINGS 1))
                                (AREF COUPLINGS 0))
                             (*
                              (- (AREF COUPLINGS 1)
                                 (SQUARE
                                  (+ (AREF COUPLINGS 1)
                                     (* (AREF COUPLINGS 0)
                                        1.6393626534254047d0
                                        -0.28157314694834445d0
                                        (+ -0.28157314694834445d0
                                           (* 1.6423813483707832d0
                                              (AREF COUPLINGS 1))
                                           (* (AREF COUPLINGS 0)
                                              -3.9117058898882657d0
                                              -3.970822355081399d0))
                                        -0.28157314694834445d0
                                        (+
                                         (* (AREF COUPLINGS 2)
                                            -3.970822355081399d0
                                            (SQUARE
                                             (* (AREF COUPLINGS 2)
                                                (+ (AREF COUPLINGS 0)
                                                   (AREF COUPLINGS 1)
                                                   (AREF COUPLINGS 0))))
                                            (AREF COUPLINGS 2)
                                            (AREF COUPLINGS 1))
                                         (AREF COUPLINGS 1)
                                         0.13694895531853568d0
                                         (AREF COUPLINGS 1))
                                        (AREF COUPLINGS 2))
                                     (ATAN (AREF COUPLINGS 1)
                                           (*
                                            (+
                                             (* 3.5783156939259086d0
                                                (+
                                                 (* 1.9322815947063288d0
                                                    3.5783156939259086d0
                                                    (AREF COUPLINGS 0))
                                                 (AREF COUPLINGS 0)
                                                 (AREF COUPLINGS 1))
                                                (AREF COUPLINGS 0))
                                             (*
                                              (- (AREF COUPLINGS 0)
                                                 (SQUARE
                                                  (SQUARE
                                                   (* -1.64550538436169d0
                                                      (AREF COUPLINGS 1)))))
                                              -0.01036753259739509d0
                                              (AREF COUPLINGS 2))
                                             -1.5139755729694455d0
                                             (* (AREF COUPLINGS 2)
                                                1.572745982753589d0
                                                (AREF COUPLINGS 2)))
                                            -0.6064861619825485d0))
                                     (AREF COUPLINGS 0))))
                              -0.01036753259739509d0
                              (AREF COUPLINGS 2))
                             -1.5139755729694455d0
                             (* (AREF COUPLINGS 2)
                                1.572745982753589d0
                                (AREF COUPLINGS 2)))
                            -0.6064861619825485d0))
                     (AREF COUPLINGS 0))
                  (AREF COUPLINGS 2))))[:EXTERNAL]

If I start up a fresh Lisp instance on the same machine and do
(COMPILE NIL <stuff>), where <stuff> is the big complicated argument
above, it apparently compiles smoothly. This is not good news :-).

I have the offending Lisp process sat at a debugger prompt.
If there's anything I can usefully do with it, do let me know.

-- 
g