slim - i tried to replicate your video issue with 9800GTX@SLI (double) by playing mkv file over the night, and it's okay. though i'm still getting weird trisli problem, need to check my bridge later.
qx9770/c1, 4x2gb @ 1600 7-6-6-15-2t, latest bios and nvidia driver for nf and gf. rest of all set to Auto.