I used to do tech support for a wireless company I think I may know a fix.
Try going to:
Control panel
Network and sharing center
Manage Wireless Networks
And then select your router name, then click on remove.
After you do that, connect to the router as you normally would and this should work.
Basically what this does is removes any settings that was stored on the computer that is causing the issue. It basically like removing the settings, then connecting to the router for the first time. Let me if this works or come on mumble if you need futher help or if you want me to make screen shots of step by step instruction.
Over 9,000 tech support phone calls a day, I know what I'm talking about I have fix many wireless issues for a living at one point in my life
