"You have not selected a valid instance of WoW to attach to!"

I am running Windows 7 64bit, WoW Set to windowed and dx9 this is what i get:

 

Ok im retarded, i had to login to start it, no wonder it didnt attach.

It is working now!

 

I get this about 20% of the time even when logged in. The trick usually is to hit login then move your char around or do something in game while it attaches. Often it won't attach if the window is in background.