I tried installing OOO and a few other minor mods and I have a ton of (!) WTF things around and I copied everything over correctly to my knowledge.
Means missing meshes.
Which means, in turn, an incorrect installation process. Basically, read your readmes, check the latest release thread for things like OOO (reading the OP thoroughly where applicable), and see where you have gone wrong.
Also, run BOSS, and read the bosslog.html text that will come up post-running.
edit: It really is the only way to stop this kind of thing happening - read the things you need to read, take your time, install mods one (or maybe two or three, at most) at a time, check to see if everything's working, go to the next one/two/three or so, use BOSS, and so forth...