Hello, I'm finally on Ubuntu, Dapper drake
The setup was really easy. I don't have any strange device connected to the PC.
The only thing that didn't work immediately was the dual monitor; I have a Nvidia 7600GS with dual DVI output with 2 BenQ FP93G.
Thanks to this great tutorial Dual Monitors TwinView HowTo By Steve Fink the setup was fast and easy.
Just 2 advices:
1) Be sure that in your xorg.conf under Section Device you have
Driver "nvidia"
and not
Driver "nv"
dunno why but this was my default value.
2) If the second monitor do not works set the horizontal resolution to twice the monitor resolution.
For example, my monitor has 1280×1024 and I had to set the resolution to 2560×1024.