Yeah, some very frustrating issues right now. Basically been sitting here for days and not making much progress. I would move us to a dedicated server at a different host but with the weekend none of them are provisioning new servers right now. Will have to try to plod through till monday. I'll see if I can make any progress for some stability until then. A real shame that things ran great for 5 months or so and now this.
Things seem improved after moving a few mega-threads from view. What I noticed was the site running fine, then a big slow down. After gaining access to the mysql database process log, every time the site went slow there would be a thread id in the queued processes. Each id corresponded to an extremely large thread. Threads like "your latest 35mm camera purchase" or the "deleted" thread. There were several Kodak ones as well. I'll get these threads back into view soon but locked down and we can create a "part2" for them. For now seems safest to stash them away. It's still hard to tell 100% if that was the issue.