This is fixed in Mac OS 8.6, and you should download the update from Apple's software updates server. Meanwhile, a work around is to disable either SoftwareFPU or Folder Actions via the Extensions Manager. This eliminates the crash for most users.
There may be other applications which use similar code to what Folder Actions uses. Such applications will also crash when quitting. Software developers have been notified as to how to fix this issue.
This article can help you locate the software update mentioned here: