GNOME panel locked in CentOS 6.0
I'm running CentOS 6.0 (32bit) with GNOME 2.30. My problem is that the Panel seems to be locked down, in the sense I cannot add further launchers and cannot remove existing ones. If I select an application from the GNOME menu and right-click "Add this launcher to panel" nothing happens, whereas if I right-click "Add this launcher to Desktop" it works flawlessly. The same if I select "Remove from panel" on an existing icon: nothing happens, despite the "Lock to panel" check-box is unselected.
I've looked at the panel keys in the gconf-editor, but I cannot find anything related to this problem. Any suggestion? Thanks.