LAN/Online Cant Connect Due too "Invalid or Corrupt Skin"?

We started a LAN World at my house with me my brother and my friend on his laptop. I started the world we all joined in at same time played for 17 hours+ and then all logged off for bed. woke up i logged on and i seen u can change skins. i changed mine by downloading the ones from a minecraft skin site i seen. i used the skins and started playing while waiting for everyone to wake up and get on aswell. my brother woke up and got on had trouble at first looking for my world to jon then we did the ip server and stuff search and i poped up.
He tried to enter but got this error "Invalid or Corrupt Skin" and didnt let him join. We then tried to opposite and had him creat a world and i tried to enter but i had to also search for him on the LAN thingy using IP server thingy. i too tried to log in and got the same pop up. What is going on what do we do? please get back to me :/