Sounds like you have a couple of wires crossed at one of the switches.
Did you add crossover wires to the second switch?
Here's a diagram of how they should be wired. See if you think yours are wired like that.
I'd be remiss if I didn't point out the small danger in doing this. If you press one switch one direction and the other in the opposite direction at the same time you'll blow a fuse, or possibly burn up a switch.