My computer connects to the wireless network for a while, then disconnects, and tells me it cannot connect because "the wireless network security key is incorrect". The key is obviously fine, it's the same key and hasn't changed! What's going on, it's driving me nuts! Oh I have Vista
You might need to go into the router with a wired connection and change the password, or even disable it just to see if you can connect. If you disable the password and still can't connect then it could be a hardware issue.
Did this just start out of no where or did you recently get a new router or something?