I was listening to a record a few minutes ago, and I noticed there was a lot of dust on top of the lid of my deck, so I, very gently (and I mean, really gently as the record was playing), wiped the dust off with a duster. Doing this caused the arm to slide across the record from inside to outside, making a disturbing noise as it went. I touched the deck so softly, I cant understand how this could happen - I dont even know why it would happen if i hit the deck hard?!?! Any ideas.