> I've got 3 LEDs hooked up directly to the pic (who
>needs current limiting resistors!); one to indicate a receive interrupt, one
>to indicate that I've loaded the TXREG, and another that blinks about once a
>second.  MCLR is tied high through a 100k resistor.

Steve, I havn't studied the details of your post in depth, but I did notice
two possible problems. First, what do you mean by LEDs hooked up 'directly'
to the PIC? No current limiting resistors? I don't know if you were joking
or not, but just because a port is rated at 25 mA maximum doesn't mean that
thats all it'll draw! Some method of current limiting is required. If the
part sources or sinks too much current it can become erratic for electrical
and thermal reasons (if the pin doesn't blow in the first place).

Secondly, a 100K pullup from MCLR to VCC is far too high. The databook
specifies 40K max. to prevent degradation of Vih due to leakage current
(+/-5uA). Could your data stream be going high due to false reset? Perhaps,
if the prescaler is assigned to the WDT, and its ON.

Regards, Dana Frank Raymond
dfr@icom.ca