Use a baby wipe to make the quick release link really clean before attempting to remove it. I have the KMC power links and cannot get them to budge until it is nice and clean, then the side plates move in nicely and off it comes.
Funnily enough, last night I took a 10 speed Campag chain off my Cannondale. I think mine used a Wipperman power link (which I noticed I had apparently put on 'upside down').
I cleaned the link before trying to undo it, pulled the rear mech forward to take the tension off the chain, and held it in that position with a piece of wood wedged gently in the spokes. I then found that a gentle squeeze of the link's side plates and a sliding motion between thumb and finger was all it took to undo the link.
I had intended to replace the chain but I measured it today and there is only about 1/32 inch of stretch/wear over 12 pairs of links so I reckon it has at least another couple of thousand miles of fair-weather riding in it before I need to put my new chain on.