Samsung Galaxy S2 — Phone not vibrating while receiving notifications.

Hi,

I got my SGS2 for almost two weeks now and sinds yesterday there's something wrong with the vibration.
When I get a text message, whatsapp message or a wordfeud, facebook, or email notification the phone won't vibrate.
I think it's a software problem and not a hardware problem cause yesterday I was using facebook chat and it vibrated whenever I got a new message but only while I was in the app. When I went back to the homescreen I would get a facebook chat notification but no vibration. When I receive a call the phone does vibrate. I did a hard reset but the problem still remains. What do I do?
I don't wanna take my phone back to the store and have to miss it for two weeks or something, but I guess it's all I can do...

The phone is not rooted. And I checked the sound settings. I even checked the settings in each individual app but all the apps have vibration enabled.