My server has recently upgraded some features such as MySQL, PHP, etc. and when I try to edit one of my blogs, I get this error:

"Got an error: Error opening file '/mt-config.cgi': No such file or directory"

Not sure what is going on. I have backed it up, so maybe it is time for a reinstall?

Well, the error's what it sounds like. MT doesn't seem to think you have an mt-config.cgi file. Do you?

I can't see how your host upgrading anything should in any way have caused this, though, unless they went around messing with your actual files.

Yes, it does have a mt-config file in my directory, and I opened it up with a text editor and everything seemed OK.

Is that file located inside the cgi-bin or outside?
Also have you checked the CHMOD value so its 755?

Yes, it's in the directory, and yes, my CHMOD value is 755

Have they upgraded the OS as part of their updates or changed the security configuration?

I have no idea, I'm guessing no...

Well this can be a result of the host implementing a higher level of security on the system see http://budgibson.com/home/archives/2007/08...e_linux_5.shtml