your model is maybe lost in space (very far away).
place a camera on your floor plan near the building and then use that 3d view to relocate your model.
As the others are suggesting, make sure you have something actually in view in the 3D. This can be done with a quick "Fit in Window" or setting a camera as suggested. But I am suspecting this is not the problem.
Your mention of "moving the mouse over the screen" suggests a screen redraw issue. Do you mean to say that the 3D image appears in the trail where your cursor passes over the window? In this case it sounds like a video/display problem. If so the usual recommendations apply. Make sure you have the latest drivers, try tweaking the settings in ArchiCAD and the display drivers, check the Grahics Card Compatibility Database.
What happens is in fact that when you look at your 3D model, you see a blank canvas. Only when you click to move your point of view anywhere else, then and ONLY in that few seconds, you see the 3D appearing!!!
What I did was to click-hold and THEN move around: in this case, the 3D remains visible, but as soon as I take my finger off the mouse button, I get again blank canvas...