Comment 9 for bug 473389

Make sure the sha1sum of iso is OK by searching the value on Google

When it fails with "checksum does not match", do the following steps

Find out which one failed
cd $usbdrive_path
md5sum -c md5sum.txt

Copy the mismatched file to you hard disk, check the checksum again.
If the checksum does not match, too.
Check the filesystem.
umount $usbdrive_path
sudo fsck.vfat -nVv /dev/sdb1 #adjust the path

Repair it
sudo fsck.vfat -a /dev/sdb1
I am not sure if the above command is the best command to repair the fs.