Why does the clock stop?

[Russ Kincaid]

So, why does it run on your test board and not on mine?
And, I don't understand CIMCON = 7, it is a register so shouldn't it be
CIMCON = %0001001 ? And what does that do?

My circuit is this: except the switch only goes to ground since I enabled the internal pullups.
Hmmm, I just noticed that my schematic is not up to date: the inputs are RB4 & RB5, the outputs are RB6 & RB7.