I've got what sounds like the same problem as a bunch of people on the forums, the entry body form isn't editable. I've scoured the forums, and I've made sure that the URL I'm accessing the page through is that same as is defined in the mt-config.cgi file and that's rendered me no luck in solving the problems.
I'm unable to disable any add-ins (what appears to be the same form of issue). In both cases, clicking on the uneditable item renders a script error in the developer dashboard of IE9:
SCRIPT5009: 'app' is undefined
mt_core_compact.js?v=4.31-en, line 284...
I'm really starting to grasp at straws on how to fix the problem. Anybody have any wizard like advice?
Reported on Movable Type 4.3

Check if your StaticWebPath directive in mt-config.cgi is under the same domain as your CGIPath (i.e. that your mt-static folder is hosted under the same domain where mt.cgi is).
I've seen it happen before that because of cross-domain javascript issues the editor broke down.
Yep, they're under the same domain, at least as I understand it. Here's what I'm seeing:
CGIPath: http://www.wideangle.ca/mt/
StaticWebPath: http://www.wideangle.ca/mt/mt-static
In the mt folder listed above there exists the mt-static folder as well as the mt.cgi file.
Nate, make sure that you are accessing MT from:
http://www.wideangle.ca/mt/mt.cgi
In other words, make sure that the URL you are accessing MT from does contain the "www." prefix, as you've specified it on your mt-config.cgi file.
You may access it from a URL without the "www." prefix.
Kind Regards,
Mihai Bocsaru
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Thanks. I've been accessing the form from the www.wideangle.ca URL (I saw a bunch of posts on the forum that talked about that problem), not wideangle.ca. That hasn't mitigated the problem. So either there's a weird redirection happening on the ISP side that I can't see or it's a different issue at play here.
Now update your mt-config.cgi to loose the "www." prefix for the 2 configuration directives and access the MT Admin from the URL without the "www." prefix.
Cheers,
Mihai
Mihai,
Looks like that did it. I lost the www prefix, put the page in compat mode, and did a refresh. All three of those together look like they finally did the trick. Thanks for all the help!!!
You're welcome Nate!
Sometimes just a hard refresh of the "write entry" page in your browser will fix it.