Can't turn off water when both hot & hold taps on

Hello all.. I had a leaky Moen single handle faucet. I replaced the Moen 1225 cartridge which seems to have taken care of the leak. Now when I have both the cold & hot water supply on under the sink I can't turn off the faucet. When only 1 of the cold/hot water supply knobs is on, I can turn off the faucet. Any ideas?

General Question
A single handle faucet
a. turns left and right (currently turns water on/off)
b. shifts up and down vertically (currently doesn't do anything)
What is each of the above actions supposed to control?

a. turns left and right (Should mix the hot and the cold water)
b. shifts up and down vertically (Should open the water when shifted up and close the flow when pushed down)

Could the cartridge be installed the wrong way?

(edit) Please don't crucify me! I did not see this thread was a couple of months old!