My encounter with this problem was with a SiS530/5595 chipset board, Bug #55843. It occurred in every instance of X. I resolved it by switching from the generic SMP kernel to the i386 one.
-- Keyboard random repeat and dropped key presses https://launchpad.net/bugs/39315 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
