Help! Converting old flat buttons to newer rounded buttons (1 Viewer)

I have Access db's that were originally created in Access 2003, I have upgraded them no problem to accdb and am using them in Access 2010.
When I create a new form and add a button it is rounded/shaded/white/blue etc - looks good.
When I add a button to an existing form, or reformat the existing form buttons (back colour Accent 1, Lighter 40%, Use Theme Yes etc) it remains an old style button (unrounded, solid colour etc).
Can someone please advise how to convert old style buttons to new style buttons - driving me mad.
Thanks!!

I have experienced the same issue. So, I put the button I want on the new form and then copy/paste to the old form. I have no idea how to get around that but it does appear to only happen on the *upgraded* forms.

I think forms created in earlier versions don't adopt theme settings and this is probably the same issue.