The one person who might have been able to help you is no longer with Symantec. I hope I am proved wrong, but I somehow doubt anyone at Symantec will offer to look at your file unless you open a chargeable support call at the very least.
Do you always close and release your USB drive from device manager before unplugging it? Most people do not and this could easily cause a file to be wrecked if it is still being written to at the time the drive is unplugged.
Although it's too late for this situation, I would recommend backing up user data with a free tool like Robocopy, to a separate hard disk, USB or otherwise, so that the original data remains uncompressed and any corruption is likely to affect one or two files and not the whole shebang. I have used Ghost for many years, well before it became part of Symantec's portfolio, and was burned more than once by an image not being recoverable for one reason or another.