In a CPropertyPage Enter key doesn't work !, but space bar works OK !. help ?

I have a CPropertySheet based application with 2 CPropertyPages. In both of these pages the 'Entery key" is not functioning. I have purposefully hided the default buttons in the propertysheet. But all other keys are working including hot keys. For a button, which has default state and focus simultaneously the 'Space' key works but 'Enter' key makes no action. Why?. I use seperate dialog boxes from the resource for both property pages.

Any ideas ? Please help.