Anyone know anything about disc brakes?

Replace QR ASAP, they're O.K. on rims brake bicycles, but disc have too much power for those quick release to properly hold onto.

tighten the little nut a bit (as pictured), then as James said, wipe it down with alcohol (take out the pads, wipe that down with the oil, then sand it down a bit to ensure there's very little contamination occur).

Ed - you are recommending wiping the pad (the friction surface that clamps the disc) with oil? That sounds unwise to me.