Samsung MM-A900 / SPH-A900 / Ace

Bought this phone 3 weeks ago, no problems so far, until last night. It was around 10:40 PM and my phone is charging, when I notice the display shows the time is 7:45 PM. I rebooted and solved the issue thinking it was a one time thing. This morning, the damn display kept showing 7:05 AM when it was 8:00 AM. Because the phone was not charging, the display should have been on, but it stayed on, regardless--it was frozen. Even when making a call, after hanging up and closing, the elapsed time kept showing! Rebooting solves this, but I wonder if I should get a new phone. Is this a common ocurrence???

Thanks!