Problem with Mirror command

As the learning curve continues, I've managed to export my model into FS2002 and view it. However...I noticed that anytime I use the MIRROR command in GMAX ver 1.2, the mirrored part doesn't rendor correctly in FS2002. The outer faces seem to be invisible showing interior faces (for lack of a better term). I love the flexibility of GMAX but it seems to have a lot of little idiosyncrasies? How do I get around this? If it involves collapsing stacks in GMAX...where do I find the command? (I read this in a post headed, "Mirror problems")
I appreciate all the help so far! I hope in the end...when the learning curve is over I can offer a cool model
I appreciate all the help so far! I hope in the end...when the learning curve is over I can offer a cool model
