TECHNICAL SUPPORT / WEB APPs BUGS

Do you normally play fullscreen / windowed?
Do you use OpenGL or DirectX?
Is login / char select window same resolution than ingame window?
Does window change size when game is loading?
Do you change window size when game is loading? (ie maximizing window)

As a temporary workaround, you could use second desktop for ingame use (F2 key by default I think).

iirc, game only modifies active desktop when resize happens, so second desktop should be fine when bug happens on loading.
When second desktop also gets messed up, then bug may happen on logout.
To detect if bug happens again, move ingame gui on desktop 1 to all 4 corners of screen, and then switch to desktop 2 to play.