Rich Text in subform doesn’t work (Access 2007)

I have problem with Rich Text Format in my memo field in a subform. Settings is set to Rich Text in the table as well as in the form but the Rich Text menu stays locked (grey).

I change the Address field that is ‘n memo on the main form (without a subform)to Rich Text Format and it works (after I change the table and field settings to Rich Text), why not in the subform?