In my case this problem appears whenever my password on the windows print server changes (once a month).
However I will not be able to print after a restart.
I always have to recreate the printer with the new password. I still have not figured out where it can be changed or where it is stored...

Anyone a better idea? The month is over again! So I'm waiting for a better solution before I recreate the printer from scratch!!!

Thanks!

please have a look into /etc/cups/printers.conf
In that ascii file the password apears in the line

DeviceURI smb://printuser:prints@workstation1/HP2100

You can edit the file with a normal editor, but you have to restart cups after
that.

May be that helps to fix your problem.

Brilliant!!!

Thank you!