I had this problem and your symptoms sound pretty much identical to mine. I
found the procedure below in another group, and it solved the problem for me
and at least a couple of other people that I know of. Apparently Vista's
"auto-tuning" networking
feature doesn't play nice with some routers. Not sure if it is a bug in
Vista, a bug in Messenger or a bug in the router firmware.

Try this:
- Click start
- Type: cmd
- Right-click cmd.exe when it appears under Applications
- Click Run As Administrator
- Type the following: netsh int tcp set global autotuninglevel=disabled
- Press enter
- Restart your computer

Regards,
David