Which editor are you using? Check your User CP
There's 3 - Basic, Standard and WYSIWYG. ISTR that Basic doesn't allow smilies (or doesn't provide the menu to put them in).
I find that Standard is perfectly adequate - I can't remember what the problem was with the WYSIWYG one, but I gave up on it many years ago.
And of course, clear your browser cache, the universal panacea.
SD