Same problem for me with the following configuration:
Ubuntu 8.04.1 with kernel 2.6.24.21, M2N-E motherboard and NVIDIA GeForce 7600 GS
I also noticed that if I disabled the screen saver but in the energy management windows enable the shutdown of the screen the screen shutdown afer the specified time, resume if I move the mouse but never shutdown again until the next reboot.
Same problem for me with the following configuration:
Ubuntu 8.04.1 with kernel 2.6.24.21, M2N-E motherboard and NVIDIA GeForce 7600 GS
I also noticed that if I disabled the screen saver but in the energy management windows enable the shutdown of the screen the screen shutdown afer the specified time, resume if I move the mouse but never shutdown again until the next reboot.