I'm seeing the same set of issues appear with different instances of P2 and wondered if anyone else has encountered these problems or can suggest how to deal with them.
On 3 different blogs, I have installed P2, tested it, and it worked perfectly. Come back the next day, and it no longer works. One of three issues has appeared: 1) either the nice AJAX highlight effect doesn't work (but the new post/comment appears); 2) click the post/comment button and nothing happens (including not seeing the post/comment on the backend); or 3) the post/comment works (with or without the highlight effect), but the post goes into the body of the post and not the title, so they all appear to be post "no title" on the backend.
The only change I made to the theme was to change a couple of font sizes, and I'm using some widgets in the sidebar.
In some cases, I have made changes like activating plugins that appear to have caused the issue. In these cases, I deactivated all plugins and reactivated them, and it worked for a short bit. In other cases, I didn't do anything but make some changes to users, posts, pages and comments, but those front-end problems reappeared.
I'm going to do some further testing and try to isolate what's happening, but I thought I'd see if anyone else has had similar experiences or a possible explanation to point me in the right direction.