I had to disable entire post search functionality as the forum archive is so large and the search is so processor intensive it was actually bringing down the website. (A lot of you may have noticed a 503 error trying to reach the site..) You can only now search for topic name. Sorry for the inconvenience.
One day I'll migrate to new system and we'll have it all back.
I'm almost sure that was the cause, someone was doing some heavy searching and database can't handle it, it's too old.. Crossing fingers that it fixed the problem ..