I reckon I got it figured, ans = 'cs4 upgrade'.
You can't natively animate a 3D mesh object created in an external 3D application inside of AE.
You can create and animate your 3D object, render it, and import it as a series of still frames, or as a movie (.mov, .avi, etc...), and then composite it over your live action footage. The same holds true for CS4.
Check out this information that blissfully exists within the help files.
The same holds true for CS4.
Hang on there, not so fast.
You can actually natively work with a 3D object inside of AE (CS4) now, but the caveat is that you have to use the intermediate step of converting it to a PSD.
The process goes like this: 3D app (to create geometry)-> PS CS4 (import geometry to work inside of a PSD) -> AE CS4
Voilà! You now have geometry that is native to AE's workspace (and more importantly cameras). It is still VERY rudimentary, and I would personally still work with an image sequence as well (RPF's!), but it is 3D geometry now working natively inside of AE. It's a step in the right direction for Adobe, anyway.