Sounds like a problem with your operating system. I have a feeling you may have a problem with the TCP stack, You may need to see either a technician for the computer or find someone skilled enough to reinstall your network or operating system.
Warning: This is a suggestion, a guide to your next possible move. The problem you describe could be anything and I cannot garentee its what I have stated. I do not want to come back hearing how my insight into the possible problem ruined your life, your chatting career or your dogs chew toy. At your own risk.
P.S. If you have no dog, I'll sleep better knowing that the dog you could have had is probably happy.
