My notebook is so god damn picky, it drives me crazy. Out of 4 usb ports on the machine, there is only one that works with new MS industrial wireless keyboard with trackball. In every other USB port the keyboard just don't want to keep the signal established or won't work at all. The most funniest thing is that I don't need a driver for the keyboard. It works with Vista and XP only. How to use other USB ports with this keyboard on Advent notebook?
Probably you had too many devices already plugged and installed than removed from the system. When you install some USB device such as Web cam is, you need drivers. When you install them, just plug in and out after. But, you will need them again if you change the USB port. The computer tracks and remembers everything. So, there is probably USB drivers cache left. Why don't you try with some advanced clean utility like nCleaner is for example. This program makes miracles.