Just to add, if you have problems importing .3ds, I found .asc 99% of the time imported no bother. The biggest problem with this is it doesn't carry over textures, but for non-textured stuff or things not made in 3DSM (.3ds files exported from 3d studio max seem to import a lot more reliably than other programs)
It was the Half-Life models I got in LithUnwrap that if it saved them as .3ds O2 died when importing it, saving them as .asc O2 imported them no bother.
There's other ways of getting stuff from one program to another, that's just the way I done it for getting some HL models to OFP (A while ago)
Hmm, this reminds I still have that HL > O2 tutorial on my hosting..
- Ben