I use Debian sid with kde 4.13 and i have a big problem.
When i try to open a external hard disk, for example, dolphin report me an error Not Authorized.
I can open and use this hard disks only with dolphin opened by the root user.
Any suggestions?

The policies concerning the mounting of USB drives are governed by UDisks - which in turn refers to PolicyKit/Polkit for authorising the user to do this. You need to ask your distribution what is needed to configure this (usually, the default shipped policies will allow the mounting of USB drives)

uh okay

Sorry I couldn't be more detailed here - the PolicyKit setup varies from distribution to distribution unfortunately, with rule files being given different names, etc so it is difficult to offer specific advice.