Daerandin, out of curiosity, I tried the command line option suggested by Majero so, in my case
sudo dd bs=4M if=/home/kladiator/manjaro-openbox-0.8.8-x86_64.iso of=/dev/sdc
after a couple of seconds this was the result:
159+0 records in
159+0 records out
666894336 bytes (667 MB) copied, 0.337927 s, 2.0 GB/s and a device called MJRO_88 is mounted.
Inside the drive there are 4 folders
EFI
isolinux
loader
manjaro
but I can't believe that 667 MB were written to the usb drive so fast and, not surprisingly, it doesn't boot.
Have you any idea what I did wrong?