When I add a new Printer, I get these error messages:
- on select a printer screen:
"Failed to group devices: 'Failed to execute program /usr/bin/scp-dbus-service: Success'"
- on select driver screen:
"Failed to search for a recommended driver: 'Failed to execute program /usr/bin/scp-dbus-service: Success'"

What is this about, does someone have these same error? And how can I fix this?

This is rather unusual - it means the executables are exiting with a status code indicating failure (ie. not 0) while printing a message that they were successful. I would suggest checking with your distribution to see if the package that supplies scp-dbus-service has any known issues, as it is quite possibly a bug in scp-dbus-service (or possibly in the code which KDE uses to interact with it).

Ok, thanks for the explanation. I'll ask in the chakra forum.