jsdIDebuggerService crashing FF 2.0

Hi.  I have a FF extension that uses jsdIDebuggerService to extract 
information about errors in eval() code.  It's working but it crashes FF 
sometime after it has done its analysis. The code is all Javascript. I 
set errorHook, debugHook, topLevelHook, and scriptHook, turn jsds.on(). 
As the page runs I store jsdIScript objects in an array but they are all 
deleted again.  I do issue dump() and send  a nsIScriptError to 
nsIConsoleService.  I also have a nsIWebProgressListener and a 
consoleListener but these have been working for a while without crashing 
the browser.
Any suggestions?  The crashes seem to happen when I do other things 
after running my code; they seem a bit random, but then I have been 
making lots of changes up to now.
Thanks,
John.