I've got a BB curve 8310, over the past week and icon have appeared i have no knowledge of, it looks like a tiny browser icon with a number 1 before it, on the top left, next to the time and date, just after the battery life.
Well I don't have myspace, but if it is anything like facebook app then it means 4 myspace notifications or messages. On the facebook app I get a friend request and it will show a #1 and the facebook icon. I believe that is what it means just notifications.