I have a feeling that SFN's servers are getting bogged down with the level of users that we have on at any given time. I've had quite a few "Server is too busy" errors thrown out by vB, and occaisionally I can't get through at all.
Knowing that SFN is on a VPS at the moment, I think there are a few possible solutions, the most obvious being "get a dedicated server." Of course, I don't know if blike is willing to shell out that much a month, so the only other possible solution would be to reduce the amount of work the server has to do. Disable a bunch of unnecessary vB features, clean up templates to decrease the disk usage/bandwidth, etc.
Hope things clear up soon.