Xperia X10 :: Cannot Receive Text Notifications?

I always receive texts normally and get the normal notifications and can read messages through normal messaging. I now cannot recieve notifications and use messaging for my husbands number. I can only check texts by going to his contact info and selecting messaging. I dont even get a notification of his message coming through. his messages don't show up in the normal message centre, although they are there when I go in from his contact