Problem with yahoo messenger?

sometimes i dont get ims people send me and they dont get mine and at the bottom it will say "_____ is typing" but i never get the im. and they cant get mine....i can see what im sending them but they dont get it. then people say that i logged of then logged back on, and it will look like my friends log off and log back on emmediately. its driving me and my friends crazy. could it be my internet service or theirs? plz help