This kind of problem is often to do with signal strength/interference. Router and computer are trying to handshake on the encryption type and password but the signal is failing as they do it. I've had this even with an apparently healthy signal but a strong wifi network on the same channel nearby. Problem is solved by disabling wireless security in the router -- but that's not wise.
You should try to optimise your reception and avoid interference.
1) raise the router above furniture level
2) Experiment with channels (some will work better or worse depending on your environment)
3) If you can detect strong neighbouring wifi, use a channel 5 stops away from strongest.
4) Relocate cordless phone base or video sender etc.
5) Be prepared to move the computer (or at least turn it so your body is not between the router signal and the wireless adapter's antenna.