Nautilus uses different permissions for mounted drives
Solution 1:
It's a bug: Nautilus says the USB stick is read only when it is not https://bugs.launchpad.net/ubuntu/+source/nautilus/+bug/1021375
Solution 2:
This Bug can fixed by:
- Removing /home/[my-username]/.config/nautilus directory and after logout and new login the problem should be solved.