Thread:Project:Support desk/Main Page edits ignored

All attempts to edit the contents of my locally-installed MediaWiki's main page are failing. I don't get any error message; it just reloads the same form with my changes removed. This is a recent development (only noticed it in the last week), and I can't figure out what could have changed on the server to cause it. I searched extensively in the forums and didn't find anything quite like this.

I was running 1.18.0; I upgraded to 1.21.1 hoping that would solve it, but nothing happened. I tried editing my LocalSettings.php to add this line:

$wgGroupPermissions['sysop']['editprotected'] = true;

That didn't help. I turned on all the error logging I can find and still get nothing. Also turned on debug logging--I can post the results here if that would help, but hesitate to do so because they're lengthy and I don't see anything that stands out as glaringly wrong.

I'm using MediaWiki 1.21.1 on LAMP; PHP version is 5.3.26, MySQL is 5.1.70-cll, Apache 2.2.24. Have spent far too much time on this already and could really use a hint. Thanks in advance!