Will there be any current with NO WIRE connected?
There will be a small current while one FET is turning off and the other is turning on. (first picture ~450ma)
I am also wondering about the Diodes.
If they are in backwards that would cause the problem you describe. Since the P Channel has the highest resistance it would get the hottest. (see 2nd picture for the very high current)
Does your simulator tell you when there are conflicts or errors? It didn't spot the GND error.
Sometimes it just won't run if it can't figure out the circuit, but usually you have to interpret the outputs to see if they are what you want. For example in the case of the ground the output went between ground and minus 12 instead of plus 12. I'm not sure it would really work that way or not.