I have also a good working HSS-800CI . Now i have updated him with the upgrades from hisat. The problem is now that i am lost everything. I have anymore image , no sound ...... Even the menu or any key works , so i have a "dead" reciever. Is it possible to upload your firmware ( bin. file ) with SatEditor and mail me once this file. Then i can download this file on my "dead" reciever and maybe he can works again. Just like you i have tried allover the internet but don't find any firmware.
Send an E-mail to the contact details of the manufacturer http://www.hdt.co.kr/eng/ they do not appear to have any software in their download section for the HSS800ci, it is now obsolete, but invite you to E-mail them for any software that isn't there..