Freightliner in 2000 used the Medallion System III gauges. They receive info from the VDC (vehicle data computer).
Sometimes various gauge malfunctions will occur, speedo goes to zero w/o affecting cruise control. Air pressure or other gauges fluctuate, and then all will reset and operate normally after vehicle is shutdown for several minutes. (reststop)
Freightliner Service bulletin on the gauges is available here:
http://ww2.justanswer.com/uploads/go...44_sbu5412.pdf
Also the VDC or VDU had a problem with cold solder connections that caused gauge problems. Article here in IRV2 files section explains the repair process.
http://www.irv2.com/forums/downloads.php?do=file&id=76
(hopefully your problem is just -everything will reset on restart)