Description of problem:
If I go into the GNOME Shell Control Centre, I cannot add a printer.

Version-Release number of selected component (if applicable):
control-center-2.91.90-2.fc15.x86_64

How reproducible:
Every time.

Steps to Reproduce:
1. Log into the GNOME Shell.
2. Click on User Name (top right-hand corner)
3. Choose System Settings from the drop-down menu.
4. Choose Printers from the list.
5. Click unlock and enter root password.
6. Click "+" to add a printer.
  
Actual results:
Nothing happens.

Expected results:
I expected some kind of input box from which I could add a printer. Clicking the "On/Off" switches in that dialogue box does not seem to do anything.

The "Options" button also remains "greyed out" (inactive) at all times.

I can confirm that Cups is running, as per:

#service cups status 
cups.service - LSB: The CUPS scheduler
	  Loaded: loaded (/etc/rc.d/init.d/cups)
	  Active: active (running) since Thu, 03 Mar 2011 16:24:14 +1000; 17h ago
	Main PID: 1109 (cupsd)
	  CGroup: name=systemd:/system/cups.service
		  └ 1109 cupsd -C /etc/cups/cupsd.conf


Additional info: