Errors in deleting plug-ins.

I get the following error from two of my three blog installations when trying to remove a plug-in:

Warning: getmyuid() has been disabled for security reasons in /home/digit84/public_html/deckchairs-themovie.com/news/wp-admin/includes/file.php on line 842

This would appear to be a security issue with my service provider, but I’ve never seen it before. To be accurate, I don’t recall having had to delete a plug-in before either.

Specifically, I was trying to install the Calendar Plus plug-in to see if it would resolve the widget overlap that Calendar has in 3.01’s default theme. I figured I’d better remove Calendar first, and that’s where the problem began.

Since the automatic delete didn’t work, I simply deleted the files in the plug-ins folder, since the way I got them there to begin with was just basic FTP.

This resulted in an error that Calendar Plus wasn’t able to re-declare something because Calendar had already declared it. That made sense if the original program was still there, but it shouldn’t have been.

I can live with the security on my web-server being paranoid driven (it’s cheap), so long as I have a manual workaround that prevents this kind of problem. Can anyone advise on the process to manually remove (and/or deactivate) plug-ins on 3.01 to resolve this problem?

I have no issues with editing code, I just don’t know where to start looking and any advice is greatly appreciated. -R