HP LJ3800 - no color output

We have an HP LJ3800 color printer that exhibits an unusual failure mode. About 1 color print job in two is produced in gray scale. Once the machine (apparently) toggles into gray scale output mode, it can be restored to color output by a power off, power on reset. In some occurrences of this problem, as many as 5 power off reset cycles are necessary to restore color output. Full resets from the control panel also will restore color output, but no more durably than power off resets. Search engine inquiries concerning this problem turn up a few descriptions of what seems to be this same behavior, but I have not read of a clear cause or a solution.

The LJ3800 is installed with a static i.p. address in a Windows network. Most of the desktop machines on which this printer is installed are legacy XP sp2 systems, all fully patched, and MSE definitions up to date. All of these machines use exactly the same pcl6 driver version. We have one Win 7 machine on this network, but the appearance of this problem preceded the Win 7 machine introduction by many months. Has anyone else who reads here seen this, and if so, is there a reliable solution?