Ernst,
I did do head replacements last week, but that shouldn't have affected anything done this week. I can understand head replacements requiring new calibrations, though.
Honza,
I did just install, I think on Saturday, a simple 3rd party clock to replace the XP one in the system tray. It provides more info by reporting day, date, hour, minutes and seconds. Perhaps this is the cause of the miscommunication.
You may have at least answered the question as to whether the printer is actually using the latest calibration despite the "obsolete' warning. This is really all that matters.
Thanks for the responses,
Jim