I just received the Third Edition 1996 Technical Library on CD from
Microchip (thanks Microchip :) and on it there were a complete
application not  (AN607) on Power-up Trouble Shooting.
I quote from AN607:


Q. The device was powered-down and then pow-ered back up, but the
device does not oper-ate. What could be wrong. A. Possibilities
include:

1. If power was applied to an I/O pin when the device was
"powered-down", the device would be powered through the I/O pin. The
internal logic is not actually powered-down, and Power-on Reset (POR)
will not occur.

 2.When VDD was powered-down, VDD was not given enough
time to settle to 0V.

3. The VDD ramp rate is too slow.
--
Werner Terreblanche     http://www.aztec.co.za/users/werner
wterreb@plessey.co.za (work)  OR  werner@aztec.co.za  (home)
Plessey SA, PO Box 30451,Tokai 7966, Cape Town, South Africa
or (Suite 251, PostNet X5061, Stellenbosch, 7599)
Tel +27 21 7102251   Fax +27 21 721278   Cell +27 837255164
------------------------------------------------------------