Emoji messgessage failure

My friend and I both have the Iphone 4s. Both of our devices have the IMessage function and Emoji keyboard active and for a while we had no problem texting until now. Every time either of us puts an Emoji in a message it appears blank. Also the IMessage function seems to disable itself so it appears as if I am messaging someone who owns an Andriod. Anyone know whats going on? I already tried looking up any troubleshoot problems on Apple support and looking at other forums but I keep stumbling upon nothing. Any help would be greatly appreciated.