Problem In Arabic Fonts

Hi Friends,

                    Their is a problem related to fonts, I m working with English & Arabic Fonts,

when i use to write arabic text after when i go to change them the fonts series named MCS & AF (Arabic Fonts)

are displayed but after selection the text changes to boxes i mean to say these fonts are not changing but some of the other fonts of arabic are coming proper, why its happening?

but when i use x5 this fonts are working so whats the problem with X6..!!!