random prop faces (w/ translucent texture) go "missing"

[kinggambit]

I've used transparent texture on props fine before, but ocassionally, I'll get issues like this:

[IMG]http://i.imgur.com/4yhlxQx.jpg[/IMG]

I thought it was that issue in games where 2 alpha textures will clash and cause problems but I don't think that's it.

Has anyone run into this issue before? (or feel free to make suggestions)