How does your node tree look?

"The only way" is an assumption of yours, careful with those, you might get in trouble one day!
You can just use the One Minus node :)

They might be related yeah. Briscoe - Are you using post FX? If yes, how does it look when disabled?

(It would be nice to have more than 8 interpolators)
Anyhow, I just noticed that there is one special interpolator I haven't used yet!
I might also be able to use a single interpolator for both UV0 and UV1

Is both your camera and the project on forward rendering?

I've noticed quite a few things currently broken with the PBL mode. IBL is a bit of a tricky subject though, because the energy conservation etc needs to be baked - I think. I'll do another pass on the whole IBL / PBL implementation soon :)

Sadly no, but I do think I have a solution. The issue is that the UV coords for screen corrds and the depth sampling are different, but I think they can be combined.

Ah, no, that is a separate issue really. Refraction and depth nodes require quite a few interpolators, and it looks like it's overshooting the limit. Tricky issue, hm