The reason this forum is so slow is because it is getting DDoSed.
If your Forumotion forum is going to get a similar amount of DDoS, Forumotion is just going to kick you off their service.
Any idea who is behind it?
Seeing as a considerable amount of Bitcoin-related sites was being attacked (I believe Mt. Gox had to turn to Prolexic?), it appears to be a person or group that doesn't want Bitcoin to exist.
Probably not Anonymous, probably not Lulzsec either, maybe a bank/government agency, but for all you know it may be one single person who owns a large botnet and just happens to dislike Bitcoin. There's not really a way to tell.