I've got a brand new clean install of Ubuntu 10.04 running on a 6-year-old HP laptop. Everything works fine with one exception: periodically (say once or twice an hour) the machine will completely freeze for a few seconds while the built-in CD drive spins into life. The mouse, keyboard and trackpad are all unresponsive while this happens, then the drive spins down again and everything comes back to life.
Any idea what might be causing this? I've installed very little on it: the only app I can think of that involves background file access is Dropbox. Might that be the culprit?