I sure hope you're using these applications for their intended, original purpose, Rob. Cutting back SP2 just for the sake of p2p applications like this is really a drastic step. Also, finding a solution from us will be like finding a needle in a haystack. There are a thousand and one things which could cause this problem depending on lots of little things specific about your system.

I suggest buying a new computer, never connecting it to the 'net and having a happy life.