Thank you, MasterC.
As you suggested, I have tried 1024x768 resolution and 85Hz. It should be enough for testing the linuxMCE capabilities.
I would buy a Nvidia card, but I have tested one (Gigabyte one with 7600 chip, I think) and it didn't work.
My motherboard (GA-8I915G-MF) has a PCIE-16 slot, but i tried connecting it there and couldn't get it to work. The BIOS does not have an option to disable the 82915G chip and there was no message of the system that detected the PCIE card, so I could not start the system from it.
I will try to see if i can get a new driver in xorg, but my linux knowledge right now -i hope that would change in the future- is not good enough to help developers to test a driver
I have triad almost all mixes of possible configuration for the MD graphics, and none work properly.
Using opengl accelerator, I could manage to get UI2 with masking (no blending) working, but it was not stable, sometimes you could get the menus and select on them and sometimes not.
Using UI1 I could reproduce a DVD, but was not very stable either.
May be it is my system configuration (the i915G graphics card) but i am not sure.
I have another system much newer, with a GA-590SLI-S5 motherboard and an AMD64 x2 5800+, but tried to install kubuntu there and it didn't work either (complains about the system timer with a kernel panic in the very first steps).
It seems to me that LinuxMCE is not very stable and mature yet, but it is a very interesting software, so i will keep trying.
The linuxMCE developers don't seem very active in the forums these days either, they must be very busy in the developing stage. More work seems to be needed in the compatibility and installation area, to have a systems easy to install in many systems.
Thank you for your help it aid me to get a working system and have an idea of the posibilities. Will keep looking forward to linuxMCE advances and trying to get a stable and capable system.