I continue to get the following error message: Unable to complete back up.an error occurred while creating backup folder. It's a brand new drive. When I attempt to repair it using disk utility I get:unable to repair disk cannot unmounted

kellyfromid wrote:

. . .

Yet when clicking on this, I only get a big ERROR message! Har! Do you suppose that's a bad sign?

Yeah, I get the big "Error 500" too. Post something on their site, or see if you can contact their support folks directly.

Well, I think I will keep the Seagate HD and just not use Time Machine on a daily basis. It seems that I will be able to back up stuff, now and then, by restarting the ol' apple, hitting "Backup Now" and then, after the backup, getting out of there before things go wrong.

I understand, but if you haven't yet, please consider Time Machine - Frequently Asked Question #27 carefully. A single set of backups really isn't all that secure. There are a number of threads here where an internal drive failed, or was hopelessly corrupted and had to be erased, and in the middle of restoring from the backup drive, the backup drive failed, too.