Not sure if this is a known bug but when you make a mistake on the License string you cannot use backspace once a hyphen has been automatically added. Also If you go back to insert a segment in the string it will go to the end of line once one character has been inserted.
This was a bug with the original SR0 install discs, I was under the impression that it had been corrected in later versions…
I believe there were other issues in the original install disc as well. If you had a computer that had XP at one time, but was upgraded to Win 7, this could trip it up. I saw that a couple times. There is a new install download on the website to replace the original.