Nudge and alerts are not working

Can someone please help me out with this one:

When i sign in to any computer it seems that my nudge does not work
properly. When i send a nudge to a contact, it tells me that i've sent it but
i don't hear the sound nor i see that nudge shake. I have enabled everything
in the options that relates to the alerts - sounds for the nudge. At home
when i sign in to my pc the nudge does not work either but when my brother
signs in to the same PC at my home, his nudge works fine. I can see the shake
and hear the sound. Is this a profile issue or what? because i thought it was
my windows live msn program that was the problem but my brother's account
works when he nudges. Please help me out here. Thanks

Morris