Barry, as you suggested I checked the surface settings and transparency was not turned on so that obviously was not the problem. The following is a copy of the email I sent to Archicad about my problem.
I am currently having an issue with what is displayed in the 3D working window. I have attached a file that currently shows the issue (at least on my PC). Now my PC has the Windows 7 X64 Ultimate OS, an i7 processor and 6GB of RAM. The video card is a GTX670 from EVGA which has 4GB of memory. I am also running V17, build 4005 of the 64 bit International Archicad software. If you open the file you should see a slab with cutouts. On my system the file opens in the 3D view. If yours opens in the floor plan view please change to the 3D view. On my system, when viewing the slab in 3D it shows the surface colour for only a portion of the top and the rest of it shows as transparent. Just for fun I did a proper rendering of the slab in Archicad and the rendered view showed properly. This issue started to show in another project I was doing and I thought maybe the issue was one of size as that project had a very large size (over 200MB file size) so I copied the slab and placed it in its own project. Got the same result so file/project size was not the issue. I noticed that the skin/texture for the top surface of the slab overlapped into the opening in the center. It should be noted that the polygon shape in the center was created as a single entity using the polygon drawing tool available in the "slab" placement option. I had tried any and all options regarding the 3D engines (both internal and openGL) but nothing seemed to solve the issue. It should be noted the when using the internal 3D engine the area that was transparent when using openGL showed the proper texture/skin but it was translucent and not solid. Since there was this area of overlap I decided to see if moving the point where the 2 semi-circles met mad a difference. What I found was that moving the point toward the outside of the slab did nothing but moving it inward toward the center of the slab cause it to display correctly. In the design where the 2 semi-circles meet the edges are tangent to each other and don't cross one another except for the tangent point. And while the polygon was made as a single entity my gut feel is that the software seems to think that the 2 semi-circles don't touch and that is causing the issue but as a single entity they must. I would appreciate it if someone could look into this for me and let me know if there is a fix. I am supposed to show this project to someone for review late Monday afternoon and I am sure I can explain the issue to their satisfaction it is always better if things are correct and show properly. Please let me know if anything can be done to help.
Please note that I made a mistake in stating originally that my video card was a GTX660 when it actually is a GTX670. I would have attached an Archicad file that shows the issue but I could not compress the file to less than 812KB which is higher than the max limit for a compressed file. What I have attached is a jpg file that shows the issue in the 3D viewer.
Thanks in advance to all that can help.