if you can connect to the internet but can't connect to gaim because of an "incorrect password," it's probably not a gaim problem. make sure you've got your proxy server setup right in gaim, if you use one that is.
if that still doesn't work, request your password with "forgot password" and make sure it's the right one. or you can create a new account to test it.
being on a lan generally doesn't cause problems like this, as i am on a lan and have setup systems before on lans that could connect to gaim right off the bat.