I should have said that my guess is that this issue is a problem in one or more of Xorg/kernel/NVIDIA binary driver. You will probably need NVIDIA's help to find out where the issue actually is though (it could be due to a subtle change in how things need to be called or the uncovering of a real bug due to new functionality or changes). If NVIDIA are able to follow someone's steps to reliably reproduce this problem themselves then I suspect they will quickly pinpoint where the issue lies.
I should have said that my guess is that this issue is a problem in one or more of Xorg/kernel/NVIDIA binary driver. You will probably need NVIDIA's help to find out where the issue actually is though (it could be due to a subtle change in how things need to be called or the uncovering of a real bug due to new functionality or changes). If NVIDIA are able to follow someone's steps to reliably reproduce this problem themselves then I suspect they will quickly pinpoint where the issue lies.