Comment 59 for bug 458334

This worked for me, in addition to previous posts I like to add point 4:

1. (re)insert usb stick, it will be mounted automatically
2. unmount it
 sudo umount /dev/sdb1
3. .. so we can format it
 sudo mkfs -t vfat /dev/sdb1
4. make sure you dont have any ISO's mounted that are too big, it seems to look at all detected ISO's in stead of only the selected one
5. start usb-creator
 usb-creator-gtk
6. select iso, make sure you dont have any 'difficult' characters in the path
7. create