Help help help please --- unable to make subs during match

As above . During a game I am unable to make subs. I am unable to drag the player as I have always done. I use the mouse pad and for some reason it has stopped working.
Any guidance appreciated or my Saturday night is ruined

BIG EDIT
It started to work again and then stopped the very next match
Now it has stopped working again. Anyone had this issue before ?

change the skin see if that helps

if not clear game cache(back up/copy it first) then try it, even verify integrity of the game etc

if no joy report over at SI bugs forums I would do a quick search there seem to remember seeing something like this reported last version of game there might be a simple fix