That can be caused by many things especially when concerning true custom creatures as there is alot of room to mess up when your not basing things on Beths work, without the files its near impossible to just guess as to what may be wrong.
Although Check
1) Collisions and Constrains.
2) All anims are correctly setup.
Thank you for responding a second time, some people just post once and leave.

I'm going to try remaking it and seeing if it works better that way. It took me a long time because I didn't know what I was doing, but now I should be better at it.
What happens in the CS is that the body mesh completely disappears (the eyes, tail feathers, ruffles, wings, and legs are still there) and the textures are gone.
But like I said, I'm going to try to remake it. I probably did a lot of things that I shouldn't have with settings on the meshes and stuff because I was looking at a Blender tutorial that wasn't for Oblivion (I know, not the smartest choice), so a number of things could have been different.
Thanks again!
[Edit]
I have no idea why my weight painting isn't working. No matter what setting I put it at it acts like it's 100% weight painted... any idea why?