I was having issues after an install.
First download was stuck at 22%. I went in and ran GW2 on Windows XP Compat and it booted up but then the real trouble started.
After pressing play it the launcher would crash and ask me to send a report, I found that Mumble’s overlay was messing with the start up. So a hint for those people running Mumble and having issues with launching GW2, turn off mumble or overlays before launching the game.