Jochen, success at last! I tried a burn at 18X. Zero C2 errors and zero C1 errors.

I walked out to my car, turned on the ignition, took out the map disk, put in the new disk, and watched for about 5-1/2 minutes as the update proceeded. It ended correctly, and my screen now shows level 3-1/63. Mission accomplished!

Thanks a million for all of your patience and help, Jochen. I truly appreciate it.

I will send my upgrade CD free to somebody here if you want to try an upgrade on your MKIII. I will not be responsible for any outcome, but the CD does seem to have worked for me. You can send me a private message if you like.