Limited connectivity can be one of the following:
modem - unplug for 10 secs and plug back in
Wireless Zero Cofiguation (WZC) needs to be restarted: type into the run box 'services.msc' without quotes. Scroll down to the wireless zero configuration, right click it and select restart.
In Vista the WZC is very buggy.
Should this not work then its time to check the cables and also reinstall the ethernet driver from device manager.