Not that I think is an issue for you, but nice to know that windows has a 10,000 object limit. Sounds like a lot, and 10,000 is a lot, but a lot less than you think. Especially when it comes to games. What other applications you got open when you running preview? It all adds up.
But it could be anything really.
Does that 10,000 limit include animations as well? If so that's a major bummer.
I mean, look at this interview for Baldur's Gate II
Q: How many frames of animation are there in the game?
A: : At last count there were roughly 108,420 frames of character and monster animations rendered for Baldur's Gate at BioWare for your viewing pleasure. We are adding 171,000 more frames for BGII:SoA. This does not include things like animated water, waving flags or other animated objects of any kind.
And that game came out in 2000. That was 15 years ago.