If you are having difficulties getting Vista to run consistently over the internet, and your computer is sitting behind a router or other network device doing firewalling, you may want to look at the autotuning feature and turn it off. The general idea of this feature is pretty cool, it checks the network connection on a very regular basis to see how large a packet it can send, optimizing network performance. The rub is that many routers and other network gear that supports firewalling features don't appreciate being pinged all the time and may end up dumping your connection after a while. Microsoft's own document about this feature and how to turn it off can be found at:

http://support.microsoft.com/kb/934430

the syntax for turning the feature off at a command prompt is:

netsh interface tcp set global autotuninglevel=disabled