Cannot mount volume on Linux OS

Hi all,
I started using Linux OS and I am a new user of this OS. This may be something normal but I have to ask.
When I connect USB or iPod I got an error message. What should I do?
Thank you Rene
Error:
Cannot mount volume.
Error org.freedesktop.DBus.Error.AccessDenied.
Details
A security policy in place prevents this sender from sending this message to this recipient, see message bus configuration file (rejected message had interface "org.freedesktop.
Hal.Device.Volume” member" Mount" error name “(unset)” destination “org.freedesktop.Hal”)
