Hey, I see a lot of people QQing about their 2.4 not working. Here's a step by step "guide" on what to do.
1. First off before you do anything, run a repair to see if it'll fix it. If not, then read ahead.
2. Delete your patch.mpq
3. Go to Patch mirrors - WoWWiki - Your guide to the World of Warcraft and select your favorite website to download your 2.4 at. Mine is Filefront
4. Wait until your download is finished. Move the 2.4 patch into your WoW folder, and execute it. Wait until it's done installing.
5. After that, open up WoW, and your MPQ's should no longer be corrupt.