A important (IMHO) suggest:
Why nVidia don't change a default setting of VBlank to enabled?
The VBlank off, cause many problems with videos tearing... and for not expert people is difficult try the workaround (check http://www.nvnews.net/vbulletin/show....php?p=1894576
nVidia 180.22 driver seem to be stable
Ubuntu 8.10 x64, Zotac 8800 GT AMP!, Q6600@3.2GHz, P5Q Deluxe bios 1702.