Ok, I just got WA, and installed them, went to play single player, quick match against computer and when it's loading the screen goes blank. No nuclear sign getting filled up...
My computer: 1.73 ghz, 512 MB, Ati Radeon 9200

Get the latest update from http://wa.team17.com , 3.6.28.0. So long as you have a working internet connection all through the installation of the update, that is the only file you will need.