Hi Jim,

I think I might have found a solution...

I have a 0.1uF decoupling capacitor and pull-ups on, with no WDT. The Power Up
Timer is active, and the Oscillator Timer is always on since I'm using a 4Mhz
Crystal (XT mode). The regulator seems fine at 5.05v.

I have found though that when I apply power while MCLR is low, wait a couple of
seconds, then let MCLR go high through a pull-up resistor, it works every time.
This could mean that the power line takes that long to stabilize, which is very
strange! I could work around this problem by actually attaching my ON/OFF
switch to MCLR instead of Vdd, and then the device would simply always be in
reset when 'off'. Do you think this is a good idea? It seems to solve the
problem.

Thanks for the ideas.
Graham