I have similar problems with an Nvidia 7300 GT graphics card. Nvidia driver is 100.14.19. Sometimes if I walk away for a few minutes I come back and the screen saver has not activated but the screen is black and the keyboard is unresponsive. My only recourse it to power cycle the PC. This machine started out 18 months ago with Dapper and has been upgraded to successive Ubuntu versions since, to Edgy, then Feisty and now Gutsy. I did not experience this behavior in any previous version.
I have similar problems with an Nvidia 7300 GT graphics card. Nvidia driver is 100.14.19. Sometimes if I walk away for a few minutes I come back and the screen saver has not activated but the screen is black and the keyboard is unresponsive. My only recourse it to power cycle the PC. This machine started out 18 months ago with Dapper and has been upgraded to successive Ubuntu versions since, to Edgy, then Feisty and now Gutsy. I did not experience this behavior in any previous version.