I've had it in the past where the smilies have inexplicably failed to work for a while. You can always type in the code - i.e. : plus ) =

By the way, just for future reference... I'm not sure queries like this are appropriate to the teachers forum

though I don't suppose the mods will ban you for it

but you'd also be more likely to get knowledgable help from computer-y folks in the Cafe I think.
My smilies have always come back eventually - hope yours do too!
edit: if you want to know what code to use for which smilies, if you hover your mouse over the smilie you want, you *should*

get a little java thingy in the bottom right hand status bar of your browser which will say "emoticon" and then have the right code in brackets. But if it's the java that's gone funny that might not work... you can always use the preview post function to check if they have come out how you expect.