I'm not sure if this is the same problem, but check your stuffplug options - you can bring it up by typing
/xspoptions in any conversation window or through the toolbar:
Plus! -> Preferences -> Plugins -> StuffPlug-NG (make sure this is ticked) -> Configure
Make sure
Enable all custom emoticon shortcuts is ticked, then click OK. See if it allows you to pin/unpin, and please let us know if it works.
farah050, your problem is different - you can read
this thread for a possible fix (problem no.2) or reinstalling Messenger should solve the problem.