Major trouble with TwinView

[phil-ou]

I have X running correctly with one monitor (LCD), but I'm unable to configure TwinView .

More details :

I have to reduce Horiz & Vert ranges to have X running on 1 monitor ( both are LCD viewed by the driver as CRT ). Each monitor have X running separety, in these conditions ...

But when I want to enable TwinView, the given technicals Horiz & Vert ranges, X can't start ...
I tried many settings of Horiz & Vert ranges, but no changes, except if I reduce drastically ranges to the second monitor and then, I have X running on just one monitor at a very low resolution with a desktop wich is very larger than the screen ..