bt acpi=off You probably already tried that but figured I would post it.
is what fixed it for me though in basktrack 2 I also had to turn off the video card memory (think they call it sideport or sidepost in the bios) and just used shared memory. BT3 fixed this issue for me and mine was a ATI 200M. as far as the desktop one with Nvidia I would guess you need the nvidia.lzm from the main wiki page http://http://backtrack.offensive-security.com/index.php/Main_Page
and re-burn the iso with the nvidia.lzm? <not sure on these steps I know they have gone over in the wiki and forums.
I am tempted to give this a go as my home desktop and computers at school both have the problem you describe. However I am going out of town through the next week so it will have to wait.