Odd issue with the ATT G3 model and alarms set to go off at 6:00 PM topic

To put it very simply, when I use the stock alarm clock or even a 3rd party alarm clock app, when I have an alarm set to go off at 6:00 PM on the stock clock...the phone reboots. When I use a third party app...the phone will not wake up to allow me to silence the alarm. Anyone else having this issue?