One of my clients is having exactly the same problem; however, in this case, whenever one selects “Train as Spam” from the menu, the scriptrunner process crashes. Following is a partial report from Console.app.
I only tried one particular message, but my client reports that it is happening with all messages she attempts to mark as spam. I did try re-installing SpamSieve. I even removed the entire SpamSieve directory under “Bundles” and re-installing. Nothing changed.
I’ve seen this crash several times before. In those cases, it happened only with certain messages (typically very large ones). My guess is that it’s caused by a bug in AppleScript, so I would not expect reinstalling or changing SpamSieve to help.
If it used to work fine for your client, but now it consistently crashes, I’d suggest trying to find out what’s changed on her Mac. It might work in a fresh Mac OS X user account or after reinstalling the OS.
Secondly, I’d be interested to know whether the crash happens if you train SpamSieve by running the attached AppleScript in Script Editor rather than via Mail’s Message menu.