Display Values of predefined properties in XML Forms

In EP60 SP11 we have created several XML Forms with XFBuilder. In these forms several metadata properties are used which have predefined values available via a metadata extension. Everything works fine, except for the display of the predefined values. The "Show" and "List" forms of the XF Project display the value keys in stead of the value labels. For example, the value key "countries_EN" is displayed in stead of "United Kingdom". This problem also seems to be eminent when using static combo boxes. How can we proceed in order to have the value labels displayed in stead of the value keys??

Thx Caspar