I know that there has been a lot of site downtime the past few days, and I want to sincerely apologize. We've been working around the clock trying to get to the bottom of it, and think we finally have figured out the cause tonight. We're going to give it a 24 hour tryout and hope that there are no issues, and then we can call it resolved. :)
In the meantime, I am hard at work at the office -- yes, at 10 pm on a Friday night -- trying to work on speeding up the web servers a bit by optimizing code where it counts. Once we're sure that we've solved our database issues, we're going to be putting two additional memcache servers online, and then the plan is for me to spend some more time optimizing code putting as much into memcache as absolutely possible. Anything we can do to take the load off of the database servers!