Unable to mount USB drives - Not authorized

[Frank]

Hi 

I'm running 10.04. USB pen-drives and hard disk were accessible without
any problem. 
I ran the recommended security updates + kernel updates that popped few
days ago. Now it wont mount any of my USB pen-drives or USB external
hard disks.
On Nautilus, when I connect the USB drive, a message pops up:
"Unable to mount [device name] - not authorized".

Any ideas?

Thanks!

Frank