Yes, the batteries are dead. I charged it up and turned it on and it promptly turned itself off again. The Garmin of course. Aaaaaaauuuuuuuugggggggghhhhhhh! IT'S LESS THAN THREE WEEKS BEFORE THE MARINE CORPS MARATHON!!!!!!! I mailed it in, what else could I do. The Garmin service agent said I'd have it back in 10-14 days. I'm not so hopeful. I'm pretty much hopeless.
Maybe my batteries are somehow cosmically linked to the Garmin's batteries. Somewhere in the past three years of use my electrical system has been linked to the unit on my wrist. It's like I started myself up on my marathon paced run today and turned myself off just as quickly. Five measly miles. Didn't seem to really have it physically; maybe mentally as well. This isn't unprecedented; it usually happens once or twice in each marathon cycle. This is the first time for this marathon, I guess that isn't so bad. So I just shut it down to have a better workout next time.
All in: 5 miles at 7:53.