Yes, I´ve had similar experiences with intel 950 gma graphics card running VL with upgraded X. It just randomly switches off 3d rendering. Probably a nasty bug or something, So far I havent found the solution for this. Anyways, reinstalling X did sometimes restore 3d accelleration, until it switched off again. I´ve had no similar experiences with other distros.
This was with 5.8 STD & using packages M0E´Inx built.