Private Thoughts Made Public

I’ve been playing around with the set up of my blog a lot over the last week or so. No idea why, I just got into the mood to see what was out there I could bolt on to it. I’ve added the Blogroll, I’ve added a hack to save and rebuild templates in one go, and I’ve added a plugin which should close all comments on posts more than 28 days old. This last one is a further attempt to reduce the ridiculous amounts of comment spam I’m getting.
Unfortunately, instead of getting a dozen or so emails a day asking me to approve spam comments (or not), I’m now getting an email every 15 minutes telling me there’s an error somewhere in the code. And for the life of me, I can’t find where the error is. So, if anyone else out there uses a Movable Type 3 blog (and there are one or two of you out there, I know) and have a cron daemon set up on your server, and you’re also getting this error message:
Subroutine approve_comment redefined at lib/MT/App/CMS.pm line 1996.
can you please tell me how to fix it? I know a bit about Perl, but not enough to be able to decipher 5000 lines of code in a couple of evenings, so any help would be appreciated. Ta.