Information Entered is Invalid

I'm sure this has been addressed before, but forums aren't conducive to finding information easily. I'm trying to log into the Lordaeron WOTLK server but the client keeps telling me the information I entered is wrong. I've just recently reset my password, I'm using my Warmane ID and not my email address, my realmlist is correct, and I'm not starting the game with Launcher.exe as that's not even within the game files I downloaded.

The worst part is that this is only happening on my new computer. My old laptop can log in with the same information just fine, and still has all my characters.
Could this be an issue related to how many computers I can play on? Any help would be appreciated.

where did you get that Wotlk client? Warmane?