I installed Ubuntu 9.04 on my Compaq nw8440 and had strange touchpad jitters where the mouse cursor would slow way down, then speed up. It was very annoying. The keyboard also ignored every few keys, which was even more annoying.
I installed Ubuntu 8.10 after learning that the video card drivers had changed in 9.04, but I got the exact same behavior. I searched high and low and found people with the same or similar issues, but none of their solutions fixed the problem.
I had about given up on running Ubuntu on that laptop when a coworker suggested I upgrade the BIOS. A newer one was available so I upgraded and that fixed both problems.
Sometimes it’s the simplest things…