Before going any further, get a small fan or any fan you may have close and put it over the top of the box meanwhile. Why using the serial port to update? Do you have a blank screen?? No Video? I suppose you have a S10 late model without Component Output probably just HDMI and Analog Yellow/Wht/Red???? Try to find an old small TV and make both connections (HDMI and RCA connectors) Either one should give you video (probably faint but readible). Once you find video go straight to the MENU area. Go to the SYSTEM SETUP press OK and go to TV SYSTEM. Arrow right or left on VIDEO RESULUTION until you get VIDEO on your TV using the HDMI (Probably by 1080i_60). Now that the video is properly set go back to the TOOLS section and do a factory Default. Once it finished you can go ahead and load your firmware version (Which one I can recommend: OpenboxS10-20110719 from here
Download / Software_Shenzhen Yojia Technology Co., Ltd.). Do your sats configuration ports and scan them. Wish you the best.
Do some arragenment to get a small fan so you can keep it over it 24/7