I don't know exactly what the answer is, but I can provide some suggestions:
1) try (a) uninstalling and reinstalling the hardware, (b) updating the drivers, or (c) reinstalling the existing drivers.
2) try uninstalling and reinstalling WMP9... however, doing this means you'll probably have to redo your library (if you have one)
3) visit the windowsmedia website or support.microsoft.com and look for answers there
4) visit the manufacturer's website and see if there is any support regarding the issue
Good luck!