Hopefully someone has encountered this before and has a quick answer for me.

I am combining 2 armors: the jacket from the wasteland merchant armor - edited to remove the stuff hanging from it - and the pants from the merc grunt outfit. I used Blender to do the editing. I have already edited the jacket portion of the merchant outfit successfully to remove the stuff I don't want, and that edited version of the merchant outfit comes up just fine in-game.

Now, the modded outfit (merchant jacket+grunt pants) exports out of Blender fine with no errors and looks great in nifSkope, but, when I look at it in the preview window in the GECK, as I rotate the armor in the preview window, parts of it appear and disappear. The shape is fine, the textures are fine, there's no distortion, it is just that parts of it appear and disappear as I rotate it. If I lower my view to shoe level and I look up, everything appears as it should. In game, it cannot be seen at all.

The textures I am using are the vanilla textures, off the compressed textures.bsa file.

Again, I am hoping someone has encountered this before and has already found a solution. This is teh first time I see this particular behavior in either Oblivion or FO3. I've never seen it before in all of the other armor/clothing sets I've modded.

What does it look like in-game?

Can't see it in-game. I can only see it in the GECKs preview window, but as I rotate it there, parts appear and disappear. No distortion, , textures are fine.

I know next to nothing about modeling so can't really help, but I did remember http://www.gamesas.com/index.php?/topic/1093042-nifskope-problems-i-think/ which sounds like the same problem, you could try PMing that guy.

I had just been having the same problem a few days ago. It was because I botched the NifSkipe transfer process.

I appreciate everyone's responses. I found the problem. I can't believe I didn't notice it before
As reference:
My problem was twofold: a ) I had 2 Scene Roots and b ) two NiNodes needed to be renamed (renamed jacket and pants to upperbody: one was named arms0 and the other upperbody00 .. didn't realize that made a difference before)
After I re-exported the mesh in Blender - it exported properly with only one Scene Root -, and renamed the NiNodes, I can see the armor in the GECK just fine.

Thanks again.