How do I wire a 1/2 switched receptacle?
At least one of the tabs on the old 1/2 switched outlet (the hot side) must have been snapped off, or it couldn't be 1/2 switched, it would have to be all switched. 

You describe only 3 wires (2 whites + one red), but there should be 2 non-white wires: one always-hot wire for the unswitched side of the outlet (should be black), and one switched hot wire (could be red or black) that comes from the switch for the switched side. I'm assuming that it is not a switched neutral circuit (which is uncommon and generally not safe).

Did one of the white wires have black tape or other marking to signify that it's actually a hot? Maybe one of those white wires is actually a hot wire, which, if you're putting them on the same side of the outlet would explain why the breaker keeps tripping since you'd be shorting the white-hot wire to the white-neutral wire. Even if it's not marked as hot, the marking may have fallen off (or it may never have been marked).

One way to test for this is to disconnect all of the wires from the switch and let them hang out of the box, tape or wire-nut the exposed ends of all wires, then turn on the power.

Then, use a non-contact voltage tester to see which wires are hot, flip the switch to identify the switched hot. If you do find that one of the white's is actually a hot wire, mark both ends securely with black tape.

If you do find out that one of the white wires is an unmarked hot,make sure that both of the hots (the switched hot and unswitched hot) are coming from the same breaker, if you have hot wires from 2 separate circuits sharing one neutral, you could have an unsafe condition.