I had the same problem, with a pendrive and with an ipod. After reading some info, i got that the point was in the program "pmount" that I could not execute, even if I belong to the group "plugdev". So the solution was making chmod a+x /usr/bin/{p,pu}mount Now everything works correctly, except for cdroms, which I think is due to the presence of "/dev/hdc" in the fstab.