PLEASE NOTE: That these Fixes are all based on a Windows 7 Install, I do not run Windows XP and can not guarantee that the Folders and Files referenced will be in the exact same locations.
ALSO NOTE: That these Fixes will most likely not result in a Repaired Install unless they are ALL completed. I have tried variations of these methods and the most effective, least frustrating method of resolution is to complete them all in one go.
1) Navigate to your World of Warcraft Install. By default his could be located at "C:\Users\Public\Games\World of Warcraft", "C:\Program Files(x86)\World of Warcraft". or "C:\Program Files\World of Warcraft".
2)Rename your Fonts, Interface, and WTF Folders
3)Open the Folder named "Data" and Locate the Files "World.MPQ" and "World.MPQ.lock"
3)Delete BOTH of these Files
4)Navigate to C:\ProgramData\Battle.net and Locate the Folders "Agent", "Client", and "Setup"
5)Delete ALL THREE(3) of these Folders
6)Open Control Panel and Navigate to Systems and Security and locate the Option "Allow a program through Windows Firewall" under the Heading of "Windows Firewall".
7)Click the "Change Settings" button IF the "Allow another program..." button below is grayed out, and then click on the "Allow another program..." button
8)Click the "Browse" button and navigate to your World of Warcraft Install Folder (Referenced in Step #1)
9)Select "World of Warcraft Launcher.exe" and Click "Open" and then "Add". This must be REPEATED for both "Wow.exe" AND "Wow-64.exe". (Wow-64.exe only if applicable)
10)Right-Click your "World of Warcraft" Desktop Icon and Choose the "Properties" option.
11)Navigate to the "Compatibility" Tab and Check the Box for "Run this program as an administrator" under the "Privilege Level" Heading. Click the "Apply" button and then Click the "OK" button
12)Start World of Warcraft from your Desktop Shortcut. "World.MPQ" will either begin to download right away or after a short setup runs after you select "Play" that will then download "World.MPQ". "World.MPQ" is a roughly 3.13 GB file and will require 10-20 minutes to download.
13)Attempt to load a character in to the world and run around any areas that have been crashing you to validate that the repair was completed successfully.
14)Close the game and re-enable your addons by deleting the newly created "Interface" and "WTF" Folders and renaming your previously renamed Folders (step #2) back to the original.
15)Repeat step #13 and you should be good to go.
Adding links to responses where I've tried to catch most of the issues and the concerns provided throughout the thread so far. As the holiday weekend is now over, supporting this thread so determinedly may be beyond me starting today. I'll give it my best, but don't get discouraged if your post goes unanswered for a while.
IF THESE FIXES WORK FOR YOU: Please rate this post and then link to it in other threads where others are experiencing similar issues. Hopefully this thread's new Blue tag will get it more attention and help more people. Thank you all.