Ribbon does not work in my form

In my form_open, I have:

If Val(SysCmd(acSysCmdAccessVer)) = 12 Then
Me.Properties("RibbonName") = Me.MenuBar
End If


but in office 2007, when I start the form, i get:

can't run the macro of callback function 'AA_loaded'...


How can I solve this please?

Thanks!