I had a Belkin G card do the same thing. It suddenly stopped working
in my laptop that it had been installed in, but worked if I installed
it in another laptop.

If you haven't already, try inserting it in the other slot on the
laptop. Believe it or not, this has worked for me.

Next, if no joy, uninstall it using free "Revo Uninstaller" (google
it). Do their maximum strength uninstall to remove all traces of the
driver and utility in the registry.

Then download and reinstall the most current driver after a reboot.

Steve