Hi, Picn' ...

QUOTE [ and I'm using a 100 Ohm resistor between the input pin and Vcc on each PIC. ]

Wonder if there is really ONE resistor for EACH Pic ...

Logically, there must be only ONE resistor in series with your probe ... so, the second PIC input must NOT have a 100 Ohms resistor from +5v ...

I'm not sure ... but that can be a very good reason for misrunning ...

Alain