Bug 82065 (Closed) refers to this problem, but the summary was not clear..
The summary - to reproduce this problem - is as follows:
If running KDE from KDM (graphical boot, runlevel 5) udisks and the KDE device notifier work correctly, and USB disks are recognized, and mounted.
If running KDE from # startx command, (non-graphical boot, runlevel 3) KDE device notifier recognises USB disk, but udisks mount fails, with ''Not Authorized'' error message.
It appears that the session is flagged as 'inactive' for the non-graphical boot (runlevel 3), and the rules in /usr/share/polkit-1/actions/org.freedesktop.udisks.policy then disallow the udisks USB disk mount..
The workaround is to manually edit the <allow-inactive> rules in /usr/share/polkit-1/actions/org.freedesktop.udisks.policy, but this is - obviously - not an ideal solution...
The system should behave correctly for both runlevel 5 and runlevel 3 access, and allow USB disks to be mounted from a KDE session. Many users choose to use the non-graphical boot, as it suits their workflow better..
Sounds like a dupe of bug 820675.
*** This bug has been marked as a duplicate of bug 820675 ***