Thanks Sylvr and everybody else,
My 990 is upgraded at last!! - and it was done via USB with Steve talking me through the steps on the phone. The only thing that seemed to be different this time from all the failed tries was pulling the plug after getting the Device Restart message, rather then clicking the Master Power Switch.
Steve said this whole upgrade operation has been a learning curve for everybody.
One thing I didn't expect during the reprogramming was having to name, not rename, all the audio inputs. It would have been easier if the menu had started out with the inputs labeled as they are on the 990 back panel, but it showed nothing except TUNER. As it was I had to rename and configure two of them after guessing wrong; i.e., what I thought was TAPE turned out to be CD, etc. Has anyone else had this problem? Just an inconvenience, but unexpected.
Thanks again all, for your sympathy and advice.