Hi Kannan,
Have you Arabic language installed in your BW system in tcode SMLT? Also check in report RSCPINST and activate Arabic in it if it's already not activated.
You said it works fine for other datasource so I suspect that Arabic is already installed and activated in your BW system. Can you just verify?
Is your SM59 settings correct? I mean the unicode and Language is blank in SM59 RFC destination of your source system.
Thanks
Amit