I have an ASUS K53SV laptop with NVidia Optimus: integrated Intel graphic card + NVidia GT540M. I upgraded to Fedora 17 and I have a weird problem with some external screens, not all of them.

I tried installing Bumblebee and bbswitch to get rid of the discrete card and eventually turn it off when I don't need it. I then noticed there are different kinds of flickering, depending on:

Well, this seems the most common behaviour, even though it can change in a random way. For example sometimes it flickers a lot with power cable disconnected, and if I connect it it flickers less. That's weird.

I tried different screens and the behaviour still seems pretty random. With some screens I have similar problems, with some it works fine. I tried changing the VGA cable too, but the problem is still the same.

Even more weird, I just found out that while I have the power cable connected, the worst situation, the screen stops flickering if I run a command like grep -ir something *, that would make me think that when the cpu is busy, working pretty hard, the problem disappears. As soon as the process has done, the screen starts shaking again. Please, don't think I'm crazy :) I made several tests! I did some tests regarding grounding as well, for example plugging the monitor to an ungrounded socket etc. but nothign changes.

Do you have any suggestion how to fix this issue?

I already published this question to ask.fedoraproject.org but I didn't get any reply.