I confirm the black screen issue with Totem.

Actually it changes the contrast for all the environment, and of course using Mplayer or the gstreamer test program just after also gave back a black screen.

Therefore I had been convinced it was a driver issue (reporting a bug to Nvidia and posting on this forum), until I find the contrast setting of Totem was the cause of all that mess.

Note that I am right now using Debian Lenny.