I could not reproduce your issue, but this might be related to a bug fixed in packagekit-backend-aptcc version 0.6.8-0ubuntu3.1 If you don't have the .1 try updating.
I could not reproduce your issue, but this might be related to a bug fixed in packagekit- backend- aptcc version 0.6.8-0ubuntu3.1 If you don't have the .1 try updating.