I don't know a more elegant way to solve this, but I just mount it manually via terminal.
mount /dev/sdX /mnt/external
something like that.
It's probably some random security group/permissions thing I haven't come a accross a solution for.
Somebody on another thread said add yourself to :
plugdev, audio, cdrom, etc.
(I lost the thread, but I think that's some of the stuff he listed)
I just added plugdev today. I don't know what that does though.