Problem with spam module

I'm running Drupal 5.5 with version 5.x-1.1-2 of the spam module. When I click "mark as not spam" on a comment, that works as desired. When I click "mark as spam" on a comment, I get this error message outside of my site:

Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.

Please contact the server administrator, support@supportwebsite.com and inform them of the time the error occurred, and anything you might have done that may have caused the error.

More information about this error may be available in the server error log.

Apache/1.3.33 Server at www.hollywoodchicago.com Port 80

Even though I get that, which is obviously not desired, it does in fact mark the comment as spam. It doesn't e-mail me as the admin, though, like it should. Also, when someone enters a comment that the system interprets as spam, it takes them to that error page.

Any idea how to fix this? I see that the latest recommended version for Drupal 5.x is spam 5.x-3.0-beta1, which is newer than mine. Think I should just upgrade?