Alright, well, I was unable to find the broken script that caused the error so I decided to just reinstall IRC. I did a clean reinstall, deleting any and all files. It didn't bother me since I had v6.30 so it'd be a good time to upgrade to v6.31 anyways.

That being said, I did a clean installation of the new IRC, v6.31, and I still get the message:
MPCVID Unknown command

Any ideas or suggestions? Thanks for your time.