i92guboj's (that's hard to type!) suggestion sounds pretty reasonable; except the fact that it happens on two (presumably different) machines makes it less likely it's a machine issue, unless the machines are very similar.
Any chance you've checked on the Ubuntu forums, and/or Ubuntu bugzilla or mailing list (if there are such things)?
Perhaps try one or some of the kernel-boot-line options available when you boot it up; maybe try a/some different framebuffer modes, or maybe acpi=off or acpi=force or something(s) like that? And see if ceases (or gets worse, lol)
Most interesting, what workarounds we find sometimes. I liked your thread title! That's what got me in here