Happens to me all the time also within the following parameters: Insertion within a wall of a plug-in object accessed via the AEC Objects palette such as window (simple or complex), door(simple or complex), or an opening in wall. The insertion works fine, it's just that you have to "redraw" the screen to see the result. If you didn't know better, you would think that the object was not placed. I usually, zoom out and then zoom. It's not a horrendous problem, just annoying. And from my memory I don't think this occurred in 8.0, but not sure.
BTW - Using v8.5.1 with Renderworks installed on a 600mHz P3 with Win98 and 256Mb RAM and a 32Mb Riva TNT2.