Ack! Upgraded to 2.6, and now (even though it's turned on in the preferences), auto-discovery of trackback links doesn't seem to be working. Even worse, when I manually enter the trackback URLs, it claims to be sending the pings successfully, but they don't show up at the other user's site. :-(
Any suggestions on what could be the problem?
When I had this problem on my Mac OS X server, it turned out to be an old version of one of the Perl modules. I copied over the ./extlib directory from a full install, and everything was hunky-dory.
There's some debug code on the MovableType forums that might help you; unfortunately, I wasn't able to find it a second time. Knew I should have blogged it..
Thanks, Adam. I copied over new versions of the cgi files and the extlib subdirectories, and manual pings are working now. Will see what happens with autodiscovery.