Hi sneather, there isn't really anything in particular that comes to mind.. Maybe you might try having them export to IGES format instead and then let MoI join it at import time instead of having Alias try to join things together itself. A lot of times Alias models I think are just surfaces and not really created as joined together solids to begin with. If it's been created as a whole bunch of separate surfaces that do not touch each other very tightly along their common edges then you just won't really be able to automatically get a finished solid from something like that...

- Michael