Just noticed this problem first hand (CM7, HTC Desire Z, clock set manually): I synced my phone and my alarm clock to have the EXACT same time. My alarm went off at 7 on both the phone and the alarm clock. I hit snooze on both, which is 10 more minutes. 10 minutes passed and indeed at 710 my alarm clock went off YET my android phone was at 709. Very strange.