[plt-scheme] hash-ref: no value found for key: profile-point357

I get the subject line error message. It doesn't happen consistently, 
but goes away if i quit DrScheme and restart. I am using tcp-listen &
 (require rnrs/io/ports-6)
 (require rnrs/io/simple-6)

version 4.2.1.4-svn29jul2009 [3m].
OS: Ubuntu.

hash-ref: no value found for key: profile-point357
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