Well, the problem seems to be solved! Just sort of poking around, on Control Panel I went to Ease of Access, then to Ease of Access Center, to Set up Mouse Keys. At the bottom there is Use Mouse Keys when NUM Lock is Off. I selected that and..... Voila! The number key pad works! Now to see if that will survive a re- boot. The question remains...how did the failure of the keypad occur? I've never visited the "Set Up Mouse Keys" screen before.... Cue eerie music....
Many, many thanks to all who made suggestions. PentaxForums is a wonderful resource