I've seen quite a bit of people looking for help in regards to issues with the current battle.net system. The most common of these issues is the "unable to validate game version" bug. I've personally experienced this and trust me, re-installing did not seem like an option to me. I'd like to keep this thread updated and be able to answer any questions you may have with the new system.
Current Problems:
"Unable to Validate Game Version" when using a battle.net login.
Tested and working solutions:
Solution 1: May as well try it.
Delete your cache and WTF folders.
Launch the client and you're good to go.
Solution 2: This solution is the fastest fix and most likely to work.
Simply open your wow directory and run the WoW [Repair.exe] file.
Sit back, wait a few minutes, and you're good to go.
Solution 3: If you have tried solution 1 and 2 and STILL cannot login to the game this step is for you.
Open your wow directory and find the file, patch.mpq
This file is most likely located in World Of Warcraft/Data
Delete your patch.mpq and patch-2.mpq files.
Run WoW repair.
This fix will require you to repatch the game since the last client install, so assuming it's wrath you have to patch from 3.0 onwards.
This fix may take a considerable amount of time but arguably is faster than reinstalling.
If all else fails, reinstall. I'd be impressed if you got this far with no fix. Be sure you've tried all 3 suggestions above before reinstalling, unless you're just crazy.
More to come...?
Feel free to post any feedback, questions, or concerns with issues you're experiencing with the battle.net system or just random jibber-jabber.