Cannot change default printer

Hi,

situation:

4 physical printers (all networked) are printing OK.
3 software printers (all local) are printing OK.
1 fax faxing ok.

When I right-click on any of the above to make it the default printer,
the default printer icon will briefly attach to the selected printer
and then change back to the current default printer.
So, I cannot change the default printer.
I cannot figure out how to apply this with elevation.

Any ideas?

Thanks beforehand,

Marinus.