Comment 8 for bug 144161

Note that the modules rt73usb and rt2500usb should not *both* be loading. Try removing both modules, and then loading *only* rt73usb:

sudo rmmod rt73usb rt2500usb
sudo modprobe rt73usb

If that works for you, you can then add rt2500usb to /etc/modprobe.d/blacklist to ensure it doesn't load in future.

I have the TL-WN321G and Ubuntu Gutsy (2.6.22-14-generic), and for me this fix works temporarily. After some time (sometimes a few minutes sometimes more than an hour) the interface stops working and cannot be raised again without a reboot.

I will post some error messages later.