Don't know why but it seems to be incompatible with my mod Snow! Real Magic!.

All the snow-covered blocks become invisible:

Hey, i was gonna have a similar effect in one of my dimensions! I might tell people to use this mod for it. Anyways, thats probably because we're both changing the models. In my code, i remove every single quad that has a texture that is in the 'sky/' directory, and render that. Id have to look into how your mod does it.

I think its fixed?