I’ve been experiencing some issues with sending trackbacks in WordPress 184.108.40.206-beta as of this afternoon. I did an “svn update” to update my local wordpress folder and I was updated to revision 2612 from subversion. There’s a bug report here that relates to what I’m experiencing. It seems the latest revision, 2612 has fixed the problem for some users. Unforunately, the problem started with rev. 2612 for me, which doesn’t make much sense.
If I don’t see something new in subversion by tomorrow afternoon to fix it I’ll probably just revert back to a stable 1.5.1 install.