Touch wood, it appears everything is ok now following a server reboot. From what I can tell, speed has been good for the last 12 hours. I've put in some extra caching measures in key spots to help improve stability, which will hopefully ward off any problems for a while. We'll need to look into more performance-enhancing techniques soon. And no, don't go sending me packets of V!agra.
Hopefully this post doesn't jinx it!