Comment 21 for bug 573981

I think there are three causes here:

1. usbmount is left behind from earlier Ubuntu versions or manually installed.
    Solution: remove the usbmount package. This is probably a Won't fix bug. If the usbmount package was automatically installed in earlier Ubuntu versions, it should have been removed in the upgrades.

2. A file system error causes the drive to be mounted read only
    Solution: run fsck on the drive

3. Something gives wrong permission/user on the mount point.
    Workaround: "chown _your_username_ /media/_mount_point". Actually, this seemed to be persistent for the device the next time it is connected.