This is a fairly common problem, and there have been several posts about it. Basically, there is nothing you can do except wait for the server to re-accept your User Name and Password. I turned off my computer and did something else and came back about two hours later and tried again and it worked without a problem.

It's annoying as hell, however as I said I don't know of any solution besides waiting.
Sorry.

I was able to get back in last night after about 30 mins.  My guess is that when the game crashes, the server still thinks you're logged in.  My bet is that if you tried to login from another PC while you were logged in that you'd get this same 'generic' invalid username/password message.  It really needs to be fixed though, at the very least if the crashes aren't getting fixed, then fix the server timeout after a disconnect.  This is pretty lame having to wait...