Perhaps the problem I am about to outline is the same problem being faced by Frank Lizard.
I suspect that I do not have the correct file to upgrade the ums firmware. The file name for the file I have is: ifp890us-ums128.zip.
The archive contains only one file which is a hex file, and notepad wants to open it. So what I am saying is that there is no way this file will update my firmware if notepad opens it. So where do I find the correct ums file for my 799?