I had this problem over this past week+, read lots of posts on lots of boards like this, tried lots of proposed solutions, updated drivers, firmware, a Microsoft Hotfix that sounded like just the ticket (but it didn't work), tried some workarounds, etc., and eventually came across this, which was the solution for me:

Windows Vista cannot obtain an IP address from certain routers or from certain non-Microsoft DHCP servers

I did the fix under Resolution, and not the additional one under More Information.

I have a Lenovo ThinkPad T61 with Intel network adapters.

Everything seems to be working smoothly now.