I'm not a programmer, so I don't know how to start troubleshooting this. I have Firefox and when I submit the post the Firebug pane shows 500 Internal Server Error.
The only changes I have made recently is to upgrade WP to 3.2.1 and we installed Bad Behavior and AVH First Defense Against Spam to cut down on registration spam (they work well too.)
Anyway, my next step was going to be disabling all plugins to see if that fixes it, then re-enabling them one by one.
Anyone heard of this issue before?