The sky is flashing when i use project red, it looks like it switches between day and night every tick, but the sun stays at the same position.

I'm using the latest version(2013-12-08)

My guess is, not related to PR. Although, can't really tell, as you provided no details.

This is caused by ProjectRedLighting. I have removed and added PRL 3 times and the sky flicker only happens with PRL installed.

Using Forge 953 and PRL 4.2.0.14

EDIT:
However, with PRL removed the flicker still happens while my inventory is opened.

EDIT2:
Nvm my first edit, the flicker doesn't happen at all with PRL removed, it's surely the cause of the sky flickering.

shouldn't happen anymore.