I remember I faced the the same problem after having installed the Kubuntu 7.10. If I am not mistaken this was the complete procedure how I reached a good solution:
1) I Plugged in an USB drive formatted ntfs and waited till the drive's icon appeared on the desktop.
2) Then I Right clicked the icon, chose Properties -> Permissions and unchecked Mount as user (=No) and Mount automatically (=No) and saved the changes.
3) Then I safely removed the USB drive and plugged it again.
4) The icon appeared on the Desktop and in all applications like Konqueror, Krusader ... (the icon of unmounted USB drive)
5) When I left clicked on it for the first time in any of the above mentioned programs it was mounted read-write for me as user.
6) When I safely removed the drive its icon did not disappeared but only changed back from "mounted drive" to the "unmounted drive".
This mounting behaviour described in points 3 to 6 is stable from then.
(It would be interesting to know if it works for other users in the same way.)