A short update: I've tried with Ubuntu and I can run dom3 without problems.
Then I decided to try ramarren's configuration and IT WORKS! thank you ramarren.
So the problem was due to the use of relatively old drivers versions. I have to say that lately gentoo has been VERY slow in updating packages. I think the stable branch is behind ubuntu!
Ramarren can you please share also you xorg.conf file? A new version of the intel driver requires new options and I would like to try yours.
Well, Gentoo isn't really that much behind with packages, but rather with marking the packages stable. I mean, media-libs/mesa has been sitting on 6.5.2-r1 for years now. Anyway, my xorg.conf is here, but I haven't really tweaked it beyond changing Device/Driver to "intel" after driver update and it still works.