Ribbon for Rich Text grayed out

hi there,

I have a memo field in a subform which is a rtf, but for some reason the Rich text part of the ribbon is grayed out so i cant highlight text in the memo field. I#m using access 2010. I seem to remember a patch is needed from Microsoft but i can not find anything on the internet.

Does anyone know where or have ever heard of this patch?
cheers
Mark