I had a similar no wireless connection. I had been at a friend's house and connected through an unsecured wifi without problem. When I got home my laptop could not find the WAP wifi at all. Only one thing worked.
I did a System Restore to the restore point before I had left home. Job done.
I have also had problems where the router has been rebooted but the laptop reports no signal. NetStumbler shows the router transmitting a non-continuous signal say on/off at one second intervals or longer. Gradually the On periods increase and eventually I get a lock. No idea what causes this.
Patience is required, that is all.