>> I have four 16C74's that have been programmed MANY times.  I have not used
>> them for a while, but just recently thought I'd give them a try.  I loaded
>> them with some code and they seem to work..... well sort of.  They would
>> run for a while and then lock up for no apparent reason (they are driving
>> an LED display) sometimes they wouldn't even start at all.  I have tried
>> all four PICS with the same code, and they all do similar things, but I
>> can't get them to fail consistently.  The only thing that seems to make a
>> difference is how much I load the ports.  If I only fire a few of the LED's
>> at once they seem to lock up a lot less frequently (they still lock up
>> sometimes).  I have all of the LED's run through buffers, so I know I am
>> not loading the port TOO much.  Is this a sign that I should buy some new
>> PICS or am I missing something.
>
Do a simple experiment.  Put the same program in a NEW pic and observe its
behaviour.  If the new part behaves the same as the old parts, the problem
is not due to the age of the parts.

Remember the 'scientific method' from grade school?  :-)

-Matt