Version:            (using KDE KDE 3.5.5)
Installed from:    Slackware Packages
Compiler:          gcc version 3.4.6
OS:                Linux (i686) release 2.6.18.1

I'm running a Slackware 11 box with CUPS 1.2.4 and KDE 3.5.5. When I first tried to install a printer through KDE control panel, I set CUPS as the print system and the message "Initializing manager..." showed up. Some seconds later, the following error dialog comes up:

"Unable to retrieve the printer list. Error message received from manager:
Connection to CUPS server failed. Check that the CUPS server is correctly installed and running. Error: localhost: read failed (15)."

The CUPS server was already running and I could even install a printer from CUPS web interface and print from non-KDE apps (e.g. Open Office).

If I try printing from KDE apps with CUPS though, it shows like there's no printer installed and pops up the error dialog described above. Then, if we set the print system to something else like LPD or LPR, the printer appears again and stays there even if we set it back to CUPS, allowing a succesfull printout.

The problem repeats everytime we send a print job, always requiring a manual change from and back to CUPS, which turns out to be a major annoyance.

I could verify this problem with both CUPS 1.1.23 and 1.2.4, and since KDE 3.5.4 didn't have this problem I guess it is an issue in KDE 3.5.5 itself.