Why is my 64 GB USB Flash Drive "not a valid backup location?"

I tried to tack this on to a previous question but upon reading the Code of Conduct for this forum, I discovered that doing that was improper.  My apologies for that.

I'm running Windows 7 Home Premium 64-bit SP1, installed using Toshiba Recovery Discs (I have a brand new Toshiba laptop, when I recovered the system I opted to not have a recovery partition).  I just cleansed all the bloatware off Windows, ran Windows update until there were no more updates to get (got SP1 this way), and now I've got a fresh, clean, windows installation that's never even been to a single website.  Now, I'm trying to create a system image on a 64 GB flash drive (I won't even end up using half of it, as my SSD only has about 19 GB used, and that includes the hibernation file (I turned off the pagefile, because pagefiles are unkind to SSDs)

I asked previously if it was possible to manually create a Windows 7 System Image on a (large) USB Flash Drive, and I got two "Yes" answers from two Community Stars. (See my question here)  It is also stated that this is possible on windows.microsoft.com, here.  Note that when windows.microsoft.com states that "the system image must be saved on a hard drive, it is referring to the automatic creation of system images.  If you keep reading, you'll see that the page indicates that if one wishes to manually create a a system image, that system image may be saved on optical discs, a USB Flash Drive, or a hard drive.  If it is possible, then why am I having the following problem?

Inserted 64 GB USB Flash Drive --> Closed Autoplay dialogue --> Opened "My Computer" --> Right-clicked Drive E (my flash drive) and selected format --> Unchecked "Quick Format" --> Selected NTFS files system and 4096 byte cluster size --> Clicked "Format" and acknowledged that all data will be erased --> waited a while for format to complete, then clicked OK --> Closed "My Computer" --> Ejected my flash drive by clicking "safely remove hardware" --> Physically unplugged flash drive --> Grabbed a diet coke with ice --> Inserted 64 GB USB Flash Drive --> Closed Autoplay dialogue --> Opened Start Menu --> Clicked "All Programs" --> Clicked Maintenence --> Clicked Backup and Restore Center --> Clicked Create System Image --> (The program scans for storage devices) --> My flash drive shows up under "On a hard disk" and the words "The drive is not a valid backup location" appear under my Flash Drive being listed.  For reference, "On one or more DVDs" is listed just below the text saying "The drive is not a valid backup location."

My understanding is that what I just tried to do is manually create a system image on an NTFS formatted (with a 4 KB cluster size) 64 GB USB Flash Drive.  But it's not letting me!  I understand I can't schedule automatic system image creation for USB Flash Drives, but according to windows.microsoft.com and two community stars, it is in fact possible to "manually" create a system image on a large USB Flash Drive, which I think is what I just tried to do.  If there is another way to create a system image, even more "manually" than what I just did (I'm definitely not scared of the command line, if I need to use it I'm more than happy to do so), please let me know.

I do have a low-quaility SATA-3.0 Gbps notebook HDD in a cheap bus-powered USB enclosure, and I was able to create a system image on that.  However, I expect that device to fail shortly.  I was also successful creating a system image on blank DVD-Rs.  I did, however, just spend $85 on a 64 GB USB Flash Drive specifically to store a system image, which I was hoping to use to store Windows 7 with World of Warcraft installed (total size of C drive will be about 50 GB; I have not yet downloaded WoW; I want to overcome this obstacle first).

Any insights would be appreciated.  Thanks!

1st Edit: Added links so people wouldn't need to copy/paste to their address bar, and clarified the last sentence of the last paragraph.