I have a really weird problem with my laptop ASUS K53SV. It has two graphics card (Intel + Nvidia) and nvidia optimus, but I'm actually using just the intel one.My operating system is Fedora 16. When I connect my external screen, a Samsung 2033HD, I have problems with it. It's shaking, like it had some refresh rate problems. The actual resolution is 1600x900, refresh rate 60Hz.I tried to change the VGA cable, but the problem is still the same.The point is that the same monitor works without any problem at the same resolution with my netbook (an ASUS 1215P with Fedora as well and an intel graphic card), and the same laptop doesn't have any problem if I connect it to a different screen (samsung 24 inch 1920x1080).I just tried to boot with two different distributions: with Fuduntu I have the same problem (I suppose because it's based on Fedora), while with Ubuntu the screen is working fine at 1600x900.The following is my xrandr output. I already tried without success to change the refresh rate.Screen 0: minimum 320 x 200, current 2966 x 900, maximum 8192 x 8192LVDS1 connected 1366x768+0+0 (normal left inverted right x axis y axis) 344mm x 193mm   1366x768       60.0*+   1024x768       60.0     800x600        60.3     56.2     640x480        59.9  VGA1 connected 1600x900+1366+0 (normal left inverted right x axis y axis) 443mm x 249mm   1600x900       60.0*+   1280x1024      75.0     1440x900       59.9     1280x800       74.9     59.8     1152x864       75.0     1024x768       75.1     70.1     60.0     832x624        74.6     800x600        72.2     75.0     60.3     56.2     640x480        72.8     75.0     66.7     60.0     720x400        70.1  HDMI1 disconnected (normal left inverted right x axis y axis)DP1 disconnected (normal left inverted right x axis y axis)I can't believe it, what should I do/try? 
External screen shaking with Fedora
fedora;dual monitor