Surjer,
That is odd that you skimmer stops working when you place your hand in the tank. Are you sure that something else is not causing the skimmer to stop? I have, in all my years keeping saltwater aquariums, never noticed a protien skimmer that stopped skimming when my hand was in the tank.
Varius water additives, (Calcium, Iodine, Etc.) can cause the skimmer to skim more then usual, often times just skimming water; while others can slow or stop the production of micro bubbles, though just placing your hand in the tank should not stop the skimmer. The only thing that I can think would effect your protien skimmer if your hand is in the tank would be an oil or residue on your hand, other then that the skimmer should run just fine.