Comment 21 for bug 477256

Further tests:
I installed the xorg.conf file from https://bugs.launchpad.net/bugs/447892, comment 41, so as to see what happens if I use the VESA driver.

Without the addition of acpi=off to Grub, the laptop hangs at a blank screen with a cursor once it's got past the initial XFCE mouse screen.

If I add acpi=off to the kernel line, then it boots completely and behaves much the same as the Intel driver. That is, I still get these unexpected screen blackouts at more or less 3/4 hour to 1 hour intervals. Moving the mouse (usb) does not revive the screen but pressing an arrow key or touching the touchpad does. No data is lost, but it's a bit disconcerting.

I booted into Ubuntu 8.04 for several hours this morning, and it's not happening there, so I don't think there's a hardware fault.