Ohh.. here is a clue
If I boot up debian and then plug the stick on this is what it tells me (never seen this with an iso before)
Error mounting /dev/sdb3 at /media/roba/siduction: Command-line `mount -t "iso9660" -o "uhelper=udisks2,nodev,nosuid,uid=1002,gid=1002,iocharset=utf8,mode=0400,dmode=0500" "/dev/sdb3" "/media/roba/siduction"' exited with non-zero exit status 32: mount: wrong fs type, bad option, bad superblock on /dev/sdb3,
missing codepage or helper program, or other error
In some cases useful info is found in syslog - try
dmesg | tail or so.