Found a bug in the code? Or maybe a dead pin?

I'm working on my build using an Arduino Really Bare Bones Board (RBBB). I've got an interesting behavior here when I try to add in some tact switches for a time set routine and blank the display.

I have the switches hooked into pins 2 and 3, so that I can use the external interrupts to trigger the respective routines. Pin 2 works fine, but pin 3 toggles randomly, as if it was left floating rather than tied to high with the internal pull-up resistors.

I can't reproduce the problem on my standard Arduino board with Atmega328, only on the RBBB, which has an Atmega168. What's really crazy? The problem persists even when I just tie that pin off to the 5V supply.

By selectively commenting out parts of the code, the problem seems to be somewhere in the DisplayNumberSet() routine, but I can't figure out exactly where.

I have two theories-- one is that that fancy pointer business you have in the code is somehow accessing the register for that pin. The other is that I have somehow inadvertently killed that pin on the hardware side, and now it just floats.

Thoughts? I'll post my code in the following post.