Unexpected automatic shutdown solution

Was you phone shutting down or just the screen going dark?

Hi Phil,

Does the iPhone have the same issue when not using the new case?

This could be the Auto-Lock feature, it will lock the screen to prevent accidental touches.

Auto-Lock
+Locking iPhone turns off the display to save your battery and to prevent unintended+
+operation of iPhone. You can still receive calls and text messages, and you can adjust+
+the volume and use the mic button on the iPhone stereo headset when listening to+
+music or on a call.+
+*Set the amount of time before iPhone locks:* Choose General > Auto-Lock and+
+choose a time.+ from page 105 of the iPhone User Guide

If the issue is not related to the Auto-Lock settings, try restoring the iPhone. This article: http://support.apple.com/kb/HT1414 will walk you through restoring the iPhone.

-Jason

Could the case be so tight that it is holding down the power button and powering off the phone?

Does the case have a magnet in it?

The flip doesn't have a hidden magnet to hold it closed? It really sounds like it's the case but it's hard to understand why if it doesn't have a magnet in it. I guess I'd return the case for another.

Phil,

Was the iPhone dropped? Does it have any signs of accidental damage or abuse?

You may want to make a reservation with a Genius, at a local Apple retail store.
http://www.apple.com/retail/geniusbar/

-Jason

FYI, I have a case with a magnetic flip cover. No problems for 8 months.

BTW, you can force the iPhone off without "slide to off". Just hold the power button down for about 15 seconds. Very effective when some app has gone awry. It doesn't happen often, but it does happen.