Adobe CS4 and CS5 officially doesn't support Arabic. Instead, there is a separate ME version (Middle Eastern) which supports left-to-right languages.
This means that Adobe CS4 and CS5 will only show Arabic isolated glyphs, which don't connect as they should.
However, there is a work-around to activate Arabic support in CS4 and CS5, as it is described here:
These templates and scripts enable World-ready Composer, allowing to use Arabic in CS4 and CS5.