OK, here I am (the guy with bad news ) .

This morning my alarm UI did not ring.
I had a (forgotten) alarm at 0600 coming from calendar. This one rang and woke me up, so I pushed the stop button. Then I had two alarms from clock (0715 and 0730). As I was already awake I checked my N900 from time to time and yes the 0715 alarm popped onto the screen, but it did NOT ring. So I pushed Snooze. Then the 0730 popped up and did not ring either. I pushed Stop. Abit later the 0715 popped up agaian (no ringing), and again snoozed it. Then I checked hildon-home and it was "frozen". No widgtes updated, no email notification working. So I killed hildon-home. A bit later the snoozed 0715 alarm came up again and guess what? It rang!
So my assumption that hildon-home is somehow in the game is correct. @freemangordon, please tell me if I can provide you some logs or other info ...

And maybe I did not install it correctly: I just extracted the deb and put the library in their directory. I did not reboot (nor killed hildon-home), so maybe the old library was still loaded?