Cannot configure printer anymore [could until recently]

[aria]

System(s): 14.04 up to date.
Kernel: 3.13.0-57
Printer: Canon Pixma ip2700 (no scanner, just printer),
Driver: Canon iP2700 series - CUPS+Gutenprint v5.2.10-pre2

Hello,

Up to recently, I was able to configure the printer (change the printing quality options) for any users on any machine. Now, I cannot. Actually I can get to the configuration window, I can change the printing quality, but when I click on "Apply", a window appears, hidden behind the configuration one, asking for the root password (not for the administrative one). Whatever I do, I cannot bring this window to the front to even try the administrative password. Only way to get out from this situation is to cancel or close the printer's configuration window, which doesn't save the changes. Same thing happens if I try to save the option allowing to a list of users to print: I get the same root-password window, I cannot bring to the front.

Previously, when I still could configure the printer, I did set different printing qualities for different users on different machines. These configurations were saved during the updates (CUPS?) making impossible any new configuration.

Don't want to solve this bug by installing Canon's drivers. Looked in User Manager and KUser for a possibility to set permissions for users, but couldn't find any. Looked for a print(er) group to add users to, but again couldn't find any. All these were possible sometime in the past, now they disappeared (at least the GUI).

Any suggestions on how to make possible again the printer configuration?
Thanks,

[GreyGeek]

Add yourself to the lp group

[aria]

Add yourself to the lp group

Thanks GreyGeek.
Did this, but nothing changed. Not even after reboot.
Tried the reverse too: add lp to my group, but didn't work either.
Undid these changes.

Tried to remove the printer: same root-password window, this time to the front. Changed root to the administrative user-name and entered the administrative password, but nothing happen (printer wasn't removed). Reboot, and printer is still there.
Tried to add manually another printer: same root-password window where I changed to administrator. System responded: forbidden to display printers list.

It's impossible to make any changes to the printer. Altough I can print, but cannot change the printing options (color/BW, resolution, page format, etc.). Configuration frose the way I set it before don't know what recent update (although different settings, for different users, on different machines, all frosen). I strongly believe this is a system-permission issue (missing), although this root-password window shouldn't appear...

Does anybody have another suggestion on how to fix this bug?
Thanks,

[GreyGeek]

Yes. Install kuser and use it to edit your group memberships. Add yourself to the lpadmin group as well.

[aria]

Yes. Install kuser and use it to edit your group memberships. Add yourself to the lpadmin group as well.

Thanks GreyGeek, this did the job, adding users to the lpadmin group (only, not to the lp group too).

Actually, things got fixed automatically but only for the administrative account, when I tried to boot with an older kernel, to find when the bug came into the system. By mistake, I entered the recovery mode, and exit it at the options screen (didn't run any option like repairing broken packages, etc., just chose to restart normally). Just after doing this, I saw your reply here, and checked the users in the "lpadmin" group: the administrative account was there, but none of the other accounts. Mustn’t have been there before booting in the recovery mode, because configuring printer wasn't possible not even as administrator. I added now all users to the "lpadmin" group, and now I can configure the printer from any account. As for the "lp" group, there's no user account in it, so left it as is.

Thanks again,