Been connecting to the home WiFi since I got my N900 a couple of weeks ago. There's been no problem until this afternoon. I looked at my phone and saw that it was on 3G instead of WiFi, so I tried to manually switch to WiFi.
After a few seconds, I get the "Authentication Failed" message and am prompted for a WPA pre-shared key. When I enter the WiFi key, it tries again to connect, but fails.
This is an error that others on the forums seem to have encountered, except that I've been happily enjoying WiFi connectivity without issue for weeks and now, without warning or cause, I can't.
I even deleted the connection and recreated it, but with no success.

What should I look for that might have caused this glitch? My laptop and PS3 can connect just fine, so the problem's not on the WiFi/router end.

Restart the phone and restart the router.

Restarted the phone x3, restarted the router x3, recreated the connection on the N900. Any other suggestions?