not authorised - intermittant

Hello,
Following the unexpected dead of a hard drive IU am attempting to put my data onto a 2T hard drive using both cdrom and usb devices, but I keep being told I am "Not authorised to preform operation.
Yet if I log out and back in the same devices mount without problems.
Though minutes later I will be told I am not authorised again.
I'm using LDME mageia 3
Can someone tell me what code will fix this oroblem, please
Following the unexpected dead of a hard drive IU am attempting to put my data onto a 2T hard drive using both cdrom and usb devices, but I keep being told I am "Not authorised to preform operation.
Yet if I log out and back in the same devices mount without problems.
Though minutes later I will be told I am not authorised again.
I'm using LDME mageia 3
Can someone tell me what code will fix this oroblem, please