I just built a new PC this week, and everything works beautifully. Except for my new wireless card. It's a Rosewill RNX-G300EX and I have Windows 7 Home 64-bit. I have tried everything I could think of to fix this problem. I know others have experienced the same problem where the Rosewill icon turns black, with a big X on it, and says "Not Exist" even though device manager shows the adapter working perfectly.
I have re-set the adapter in the slot (there's only one, so no spare slot to test it in).
I have verified correct drivers, re-installed them, checked my firewall settings, disabled home groups per a previous suggestion.
Windows is fully updated, and I don't currently have a virus protector or anything that would interfere. Any ideas or suggestions would be greatly appreciated.