Issue with Fedora21 "settings" after a power failure in the middle of an update.

[Eliezer Croitoru]

Hey,

I am unsure how to even look at the system now.
I have installed a Fedora 21 Gnome Desktop on a USB disk and while 
updating+upgrading the system from the basic state (57X packages) there 
was a power failure.
After turning on the PC I have tried to turn it on it was fine and booted.
I did not tried to "verify" what happen but it was in the middle of "yum 
update" so I tried to complete the transaction using yum.. whatever the 
command was.
Now the system is after an undo but "settings" menu would not start.
It would show the basic icon and text on the top bar for couple seconds 
and then will vanish and even if I am waiting 20 minutes it's still not 
starting.

Now I want if possible to find what is the issue and maybe fix it.
I need your help and recommendations.

Thanks,
Eliezer