Try to change the length of the snooze for the alarm, my wife's phone had the same problem. When I opened the snooze menu it had a value called "choose the snooze-time" selected. After changing it to 5min the alarm clock started working again. The strange thing was that the option "choose the snooze-time disappeared from the lost.

Some people used Status Menu Extension for N9 (http://talk.maemo.org/showthread.php?t=85816) and had infinite alarm loop, and now some people have no alarm at all? Gosh, I think we tweaked and hacked our phones a bit too much, people xD

Try restoring default settings. Sometimes this is known to work for stuff like these.

if that does not help, just reinstall firmware.

Witnessed the error myself too. Looks like harmattan is build on windows 95 or so.

http://imgur.com/ZBaa0t5