Just to be sure: Do you have nothing connected to the NC pins (8, 9, 10, 11, 12, 14)? Connecting those P1 pins to GND (or VCC) or using the space to route a signal can cause the P1 to behave erratically. They really do need to be unconnected.
Also are you using P1S6/TESTMODE? There are some caveats with that pin as well.