Fedora :: Failed To Initialize Packaging Backend

Recently I started getting pop-up saying:

Code:
Failed to initialize
Failed to initialize packaging backend
This may occur if other packaging tools are being used simultaneously.
under more details i get:

Code:
There are unfinished transactions remaining. Please run yum-complete-transaction as root. I get to terminal, and as a root I try yum-complete-transaction, but it just says there are no unfinished transactions left. I tried to update thru yum, but this is what I get:

Code:
# yum update
Loaded plugins: fastestmirror, presto, refresh-packagekit
Determining fastest mirrors .....

After lots of googling, I tried:
"yum clean all",
"yum-comlete-transaction",
"rm -f /var/lib/rpm/__db*" + "rpm -vv --rebuilddb" + "yum clean all",

Everything else is working well, and I am able to update with "--skip-broken", but I keep getting this pop-ups. I use fedora 12.