Ticking noise from speakers when playing dvd (by 2 users)

Hmmm, interesting... My Cambridge Audio all-in-one Cd/DVD/tuner/amp Azur 540d is making a clicking sound when playing DVDs. It doesnt do this when playing CDs at all. The noise is audible as a fast ticking, like it's picking up the sound of the dvd spinning, while playing the movie although funnily enough it seems to stop ticking during the blank gaps between tracks e.g. when going from adverts onto the main feature.

Help! Not sure what the cause might be....