[sdiy] PIC freakout?

[Richie Burnett]

You can easily disable things like power-on reset, brown-out reset and 
watchdog reset to rule out those as possible causes of sporadic operation.

I'd punt for either:

1. MCLR pin left floating and picking up 50Hz + static, hence randomly 
resetting your firmware,

_or_

2. Some un-initialised variable or SFR in your code, that just happened to 
work the first time on the debugger because you got lucky with the power-on 
state.

So the bets are placed!  :-)  Do let us know what the cause was when you 
find it and fix it!

Good luck,  -Richie,