I am getting the same error now. I installed the latest software on 3 diferent computers and it will not communicate on any of them. One of the machines had a real serial port. I have fresh batteries in the remote too. I thought maybe the batteries where bad so I stuck a meter on them and they read 1.540v. I did a master reset on the remote and still couldn't get it to program. After trying for hours I was finaly able to get it to write once so at least I don't have a blank remote. I have some more changes to make but now it will not program again. I have been trying for hours. I held my tongue to the left.... to the right... I even stood on my head and nothing works. Right now I am running 1.12.288 which I just downloaded from URC. I just emailed Surf Remote for a working link to the software with Live Update. Maybe there is something newer available.

I tell you what, the MX is always a PIA to program. Have friends and family with MX-850s (3 others) which all get Fail! 1 from time to time.