Well if you had it working, then MAC filtering isnt switched on

(
http://www.firewalling.com/concepts/MACfiltering.htm quick guide if you wanna read up)
Did you do anything to make it work? Or did it just start working?
As strange as it sounds, it might be a hardware issue? With probably the USB port (As it works on other machines, it doesnt appear to be the wireless device)
Right - Ignore the static address, as it can pick up DHCP so we need to concentrate on why it started working, then stopped....
How many USB ports you got on that lappy? I assume two and it has briefly worked in one and not the other, Does it sit in the port ok? Not loose or anything like that?