There are two different things that might affect this as well.
For this device, there are two versions 1.0 and 2.0 Are you sure you have the right driver? Linksys by Cisco - WUSB54GSC Support
Heat. plain and simple if it is malfunctioning it might be heating up and dying (I had one of these things and it got hot)
You might also try plugging this into the computer with either a usbhub or a usb extension cord. Sometimes the computer wont reject it.