I don't know if its been answered or not (there's 19 pages in this thread...) but i had this same issue and the following worked for me: I was having the same issue where I would fire the game client, CPU suage would SPIKE to 97-100%, i would get audio in the game client window that was consistent with character select screen, but no video. Moreover, not only could i not alt-tab out, i couldn't interface with anything (no right click, no clicking on anything period, etc). I ultimately had to hardboot several times to get my rig to respond.
This worked though and i was able to play without any issues immediately after i did this.
NOW... before you do this. please understand that this will reset your hardware settings but you will also need to re-enter your login credentials if they are saved (this should only take you about 30 seconds if you're like me and forgot them and had to reset them, but still). However as soon as you fire up the client again, the folder will be re-created and populated.
Hit windows key.
type "run" - hit enter
type %appdata%/Guild Wars 2/
Delete this folder.
Fire up the client, sign in, and hit play. The client SHOULD execute as normal. You may have to go in and adjust your hardware settings to your personal preference rather than the software's detected automatic settings, but you can do that as normal in the settings menu.
Good luck, hope it works for you all! :) HAPPY UPDATE DAY. :D