With so much talk about connection problems, high ping, etc.  First I would try to use a wired network and see if that make a difference.  You can get even long network cables pretty cheap.  So even if ran temporary for a few day's to test I think it would be worth it.

After something simple would be to try SMOS ( https://bitcointalk.org/index.php?topic=1541084.0 ).  If it was a issue with windows this would eliminate it and you can test with running it off a USB stick. 

I would try those 2 things and see what happens.  Then start looking at hardware but hopefully one of two above fix issues.