Assuming that curse is coming from a ghost type. I'll laugh my head off if I see a ghost type draining half of its HP then cursing itself IF magic bounce deflects it. Does it?
Yes, Curse hits though Magic Bounce. So the Pokemon with Magic Bounce would receive the Curse, and it would not bounce it back.
Smogon lists all the moves Magic Bounce bounces back. Curse is not listed. http://www.smogon.com/bw/abilities/magic_bounce