I had already outlined a problem that I thought was a graphics glitch but as I have this problem daily I dug a bit deeper and found the following.
PROCEDURE TO REPRODUCE PROBLEM
go to 3d window
CTRL O to spin around
click on plan view quickly
3d picture might also display on plan view momentarliy
Marquee is now lost and cannot be restored without full close and archicad restart
Ok this may be more a problem for us dual monitor junkies who quickly click on 3d window then click back to plan window
But every day I have this problem unless I fully wait for 3d window to "REFRESH" after rotating etc
I've tried on several of our machines and all are the same
This happens if you click to 2D within 0.5 sec after finishing orbiting. 3D model rebuild is suspended for 0.5 sec to avoid unnecessary rebuild in case you do continue orbiting. So, please do keep a 0.5 sec gap before you click to floorplan.