When it gives error, the USB drive might not be available any more. Go to Start > Control > Administrative Tools > Computer Management > Disk Management. Right click the device and select Delete Volume. Create another volume, then repeat the process, but this time choose NTFS or FAT32 (if you previously used NTFS) and it should correctly. I used the application and it worked well.
ISO : Windows 7 ISO
USB : Kingston Traveler 6 GB Flash Drive
Operating system: Windows 8 Pro x64