Search for GParted in the Ubuntu Software Center and click on the button that says More Info. This will show you the GParted Partition Editor screen in the Ubuntu Software Center, and at the bottom of this screen is a section called Add-ons. Put a check mark in the checkboxes to the left of the three Gparted add-ons that are listed below, and click the Apply Changes button to install these three GParted add-ons:
- Device-mapper Software RAID support tool (dmraid)
- Guess PC disk partition table, find lost partitions (gpart)
- Read/write NTFS driver for FUSE (ntfsprogs)1
Then try formatting the USB flash drive in GParted again.
1The Read/write NTFS driver for FUSE is called ntfs-3g in Ubuntu 14.04.