Thanks for answering my post kryo. From your reply the following I found was particularly helpful.
Completely invisible or are they becoming white icons rather than the 3d models? If the latter, you're experiencing the tactical view, which lets you get a better view or things when you're zoomed out (the Tactical View Zoom Level slider in the options determines what zoom level it switches modes at).
I think its just the sliding bar in the options menu that is set too high.
Thanks a lot for helping out.