I tried to do a search for this and came up with a few similar issues, but not exactly the same thing.
Last night I set my alarm for 6am and put my Tour in to beside mode. This morning, when it went off (I am a chronic snoozer... ) I hit the snooze button twice, with no issues. The third time however, when the alarm went off, I picked up my phone to see what time it was and the screen was white! The alarm was still going off though. I was half asleep and kind of confused so I started pushing some buttons, and the alarm sound stopped. But the screen stayed white. I stared at it for a little bit, until the backlight turned off....and then once I pushed another button to get it to light up again, it was at the home screen.
Any ideas!?!?!? It's been acting fine all morning so far. Thanks!!