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Well, thinking that it might be the hardware, I stripped the breadboard and started from scratch making sure there was nothing left floating, or tied down to the wrong supply. Loaded the code and tested. The first two inputs (RB0 and RB1) and thier coresponding LEDs (RA1, RA0 and RA7, RA6) can be triggered until the cows come home. However triggering the any of input three or four (RB2, or RB3) causes the thing to freeze.

I'm off to try it with the 12F675's and see if that works.