Transparent background render problem

Hi!
I have problem with transparent background rendering. When I render scene with normal background, there is no problem at all, but when I select transparent background always it stops at 44% with CUDA error" Illegal adress in cutCtxSynchronize()> I’ve done some research and lowered both core and memory clocks on GPU (it was running on stock before) but with no effect. GPU is 1060 6GB. Scene has memory peak at 3,7GB.

Installing older nvidia drivers helped. Problem solved.