I found two different fixes for this problem on the FedoraForum, and using both of them together appears to have worked for me.
The first is to edit (as root)
/etc/dbus-1/system.d/org.freedesktop.PackageKit.conf
by adding one line near the bottom. You'll find a line that reads:
Code:
<allow send_interface=org.freedesktop.PackageKit"/>
and you need to add, immediately after it, the following line:
Code:
<allow send_interface="org.freedesktop.PackageKit.Transaction"/>
This change, by itself, stopped the error message, but the package manager still wasn't working. It would apparently go into an infinite loop, displaying neither results nor error message. The second fix is to edit (again, as root) the file
/etc/dbus-1/system.conf
Look for two lines (probably lines 57 and 58) which will initially read as follows:
Code:
<allow send_requested_reply="true" send_type="method_return"/>
<allow send_requested_reply="true" send_type="error"/>
Edit the top line by deleting everything between "true" and the />, so that the line reads
Code:
<allow send_requested_reply="true"/>
Then delete the
entire 'send_type="error"' line.
(It would be a good idea to save copies of each of these files before making the changes, in case you need to revert to the originals for any reason. I saved them as
org.freedesktop.PackageKit.Transaction.original and
system.conf.original.)