I can't figure out what happened, but everytime yes is typed, there is a face that is displayed in the chat box and it saying Yes, or yeah etc. How do you switch that off or does anyone know what that is?

That's because you set a custom emoticon with the word "yes" on it, go ahead and remove that icon and should be resolved .

It is a custom emoticon, either you, or someone on the computer, added it to messenger.

To change it click on the emoticon button in a chat window, then press "Show All"  Then scroll down to the face that has "yes" written beneath it, then either click "modifiy" and change the "yes " to "(yes)" or something that will not interrupt normal typing, or select "remove" to delete it completely

thanks, i'll get on it and fix it. Thank you for the quick replies