Comment 55 for bug 447892

Another thing that may work (and it is useful for us to know whether it does for you) is the 'nomodeset' option combined with the xorg.conf from comment #19. I think this is what acpi=off might be doing (in addition to turning off power management and other stuff). It seems that on some chipsets the DRI option in xorg.conf is ignored when KMS is used, (c.f. comment #6). Could you try the following two cases and upload the resulting Xorg.0.log here?
1. xorg.conf from comment #19 without nomodeset. (My hypothesis: You get a freeze, so you will have to get the Xorg.0.log via ssh)
2. xorg.conf from comment #19 with nomodeset. (My hypothesis: No freeze)