Well, I tried a solution suggested on the Mepislovers forum... I tried downgrading CUPS to an older version which made no difference at all. Then, I tried doing the same downgrade process but with some conf files renamed. The assumption being is that CUPS would not find existing config files and would create new ones. All that achieved is cupsd that will not start! I also tried different versions of HPLIP, but that made no difference either. At this point I'm considering that I may have to re-install!