Biggest problem I had moving the site (to our new VPS server) .. was the blog not working.
Readers could still view pages/entries, but the blog-interface (which allows me to create new entries) would not load.
Instead of launching the interface, the master script-file (mt.cgi) prompted a *download*. ("Would you like to download, open or cancel?")
That suk'ed .. cuz I make much use of the blog .. to help keep the home-page lean-n-mean.
(Tho I create these entries in Dreamweaver, cuz it's a far superior tool to what you find in the MT interface, far as web page creation goes. Then I copy-n-paste into MT. That's why the blog entries always come after you see/read it on the home page.)
Normally I have a plenty of tools in my Troubleshooting bag-of-tricks, but this problem left me scratching my head.
I'd never seen this type of behavior. And neither had anyone at the Movable Type forums. (I use the new Open Source version of Movable Type » v4.1.)
Not being able to use the blog was a major bummer. Fortunately, I found an article that offered a solution .. even tho it appeared to address a different problem.