Hi Roger, I have a 250 2000 and experienced the same problem. I got a second hand set of clocks, but to no avail. I studied the wiring diagram for ages, checking the fuses, connections etc., and found nothing until I checked the starter solenoid. As soon as I took off the rubber cover, it was evident what was happening. The plastic top had been melting slowly due to the connection heating up.
This is where the power comes from to feed all the controls, and power was not passing continuously causing all the clocks to go haywire.
I replaced the starter solenoid and then all was well
John McMillan, September 2013