winreless NICs are always an iffie with Windows 7. I have been fortunate enough for my 2 to work correctly....
are you using the drivers supplied by Windows?
Have you tried a Windows update to see if there are more?
If you have a version 1, here are the latest drivers, but the ones provided by windows may be the best:
http://downloads.linksysbycisco.com/...N_20071019.exe
How is it not stable? What are the symptoms?