The problems are very similar to those a site on my server had. That had nothing to do with threads though, it was a loop that was badly written, causing it to go on infinately. And this code was run on almost every page on the site, which is very active. I spent ages trying to find the problem, asking the site owner several times if they had changed anything and they promised me that they had done nothing. Had to get outside help eventually and he managed to find the problem script.
