Sound like it is a connection type issue.
If you are running P2P or file sharing then these can cause huge problems.
Firstly because half of them install spyware on your PC, second because half the downloads have spyware in them, and thirdly because they take up all your upload bandwidth.
I would recommend scanning your PC for viruses and spyware. Programs like "adaware" from lavasoft are shareware [free for personal, not corporate use], and do a good job. Get your self some decent anti virus and personal firewall software, I recommend Norton or Mcafee. They are only a few dollars or pounds, and well worth it considering how much your computer costs.
Hope this info helps man.
DrM