Advice..

[trevius]

Sounds like most of the info needed is already covered by the guys, but I figured I would add 1 small snippet in case you don't already know. When you are running pings from command prompt, the command to run an extended ping is "ping -t <ip address>". This way you can run a continuous ping to these different destinations to make sure that none are dropping packets. The default of 5 pings isn't enough to see most packet loss unless it is really heavy loss.

From what you wrote, I wouldn't doubt in the least that the problem could be with the OS. I have had weird issues on certain machines where pages needed to be reloaded more than 1 time to get them to not 404. It does sounds like you have had quite a range of issues, but it could all still be coincidental.