Ok first up, one BSOD is by no means cause for a complete re-format. It might justify a full backup if you're paranoid or a partial backup if you have important files that you don't want to lose just in case further problems develop.

If the fact that it happened when you powered off the printer after it failed to print wasn't a coincidence, it could be the result of the printer driver failing in which case uninstalling and reinstalling updated printer drivers would probably fix your problem.

Regardless of what caused it, personally I wouldn't worry about doing anything about it unless it happens again. Just make sure you follow standard procedure when working on important things such as saving regularly and keeping a backup either online somewhere or on removable storage such as a USB key (or both for the extremely paranoid, you never know, you could lose your usb).

So in short: "Just Got A Blue Screen, only once though. Should I Be Concerned?"

No, you shouldn't. If it happens again, consider doing something about it. But try to fix the problem properly before you decide to reformat.

EDIT: Also, tips on backups before reformatting: just copy everything you need into a folder and burn it to a CD/DVD/External hard drive. No point doing an image backup with something like Norton Ghost if you've got a driver problem.