I have a two monitor setup, one 22" (1680x1050 res., 16:10) and another 19" (1280x1024 res. 5:4). I've installed ubuntu 11.10 beta2 x86, and the installation worked fine, the system boot was successful. I've upgraded ubuntu from the main server, and after restart, booting with the kernel 3.0.0-13, my system hangs up with a purple screen, and than nothing happens (the system boots successful with the kernel image 3.0.0-8). Nvidia current drivers not installed, but if i install it, the situation is the same. I have an Nvidia 9600GT installed.
I tried to boot with one screen attached, I've tried each port, but no luck at all. With kernel image 3.0.0-8 the system successfully boots with each display attached, but the farther kernels (3.0.0-11; 3.0.0-12; ect.) all freezes, even one display, or multiple attached. I have two systems with ubuntu installed, and the other (with Ati HD 2400XT, latest closed drivers) don't have any issues like this, I wrote about.
Update: The problem solved by reinstalling the operatin system, without automatically installing updates during install, with only one monitor attached. After completing installation, and clean reboot, i've installed closed nVidia drivers. After all, i found it's safe to connect another monitor to the system, it's not causing any problems. Probably the situation stays like this.