ok.. i sort my issue out... it was my Router...
i bought TpLink VR600 Router which has IPTV setting and i set LAN port one for IPTV and now from 3 days Box is working great no freezing... so it seems the standard Router which was installed by our Telkom Network was not giving full internet speed to the Box.. though with same router my Nvidia Shield never had any issue for watching IPTV..