Testing upgrade from 3.4.8 to 4.1.x, unable to post

[handsoffsam]

I am attempting to upgrade my 3.4.8 board to 4.1.x. The upgrade seems to go smoothly, and generally things seem to work, but I cannot post content to the forums. When I click on the "start new topic" button, I get a 404 with a fairly generic error code, "1S160/2". I don't see anything interesting in any of the logs, but I'll be honest, I'm not real familiar with the IPB system. Before I hook a debugger up to this thing and step through the code, does anyone have any thoughts on what I might look for? Thanks,

 

robert