Unfortunately without seeing the model it's very difficult to say what the problem is.
Also what are the options you need that weren't available in 3DX4?
If the model is not rigged with bones you can try bringing it into 3DXchange5 in OBJ format. This will likely load if FBX won't.
If you still have problems please supply a little more information on the model you using and the steps you are currently taking. it may be that you are missing something out. A screenshot would help to understand better too. Thanks.
Peter
Forum Administrator
www.reallusion.com