The next step should be, as has been mentioned, to see if you have the same problem using a different router. If you do, then it may be the air card. I would put the card in another machine and see if you can duplicate the issue. If the problem appears to the the wireless side of the router, then call tech support. They will talk you through a hard reset in case some parameters got messed up.
You can also try seeing if someone else's environment is interfering with yours. Tools like inSSIDer (
http://www.metageek.net/products/ins...expid=190328-1) work great for this.
Could be many things, but stepwise refinement is the key to isolating the problem.