I've encountered the alarm problem with lpsmagic before, and 1.4.1 had fixed the issue.

Recently it happened again though, and after playing with my n9 it seems that it occurs whenever I am connected to my bluetooth stereo headset:

Disconnect bluetooth stereo headset: alarm is heard, lockscreen appears, swipe up, and stop or snooze

Connect bluetooth stereo headset: brief sound heard, no lockscreen, choice of stop or snooze available without swiping

Can anyone else confirm this?