Apple - Wifi connection has password issue with my Macbook Pro

You could try 'Forget this network' in the Airport settings through System Preferences -> Network, then reconnect fresh again

For others finding this thread because they too have the problem:

On my wife's MacBook Pro, the answer turned out to be that the laptop could not differentiate between the 2.4GHz and 5GHz version of the wireless, and if it connected to a different one than last time, told her the password was wrong. The cure was to 'split' the two wi-fi networks by adding '-5' to the 5GHz version SSID, then the Mac could tell them apart. It has the same passcode for both networks (although they could be different) and is now happy to connect to either, every time.

Why this suddenly crops up for some, is down to relative signal strength on each frequency, and maybe a new router having the 5GHz band for the first time, but with the same SSID. (That is how they are normally set up, but Apple has problems with that).

HTH someone.