We got our Captivates/Galaxy S i897 about a month and a half ago. My husband had his replaced already due to the random shutdown problem, mine took a little longer before it was also shutting down randomly every day.
I took it yesterday to a nearby AT&T warranty appliance center and got a replacement (refurbished) phone. This one will, for some unknown reason, get itself into a state where the softkeys (menu, home, back, search buttons at the button) are totally dead. Not an issue with not pressing them correctly, we'd been doing this without a problem. Then, the only way you can get back to home, etc. is to power off. We did a hard reset, problem was still there.
It was like this yesterday, even after the hard reset. Then suddenly this morning, it's fine again.
date123: - Do you remember EXACTLY when the problem started for you??