I used Solution #1 without success. However, when I went back and used Solution #2 (involving editing the registry), it worked like a charm. You can even upgrade back to 1.7.2 after retrieving your key in 1.7.1 so you can download new material. As long as you don't try and grab your key again, all is ducky. I made several copies of my key and scattered them around various machines and drives just so that I would always have available in case I did something stupid, like double-clicking the wrong file.
