Without a diagnostic copy of your return it would be hard to know why you can't eliminate this entry altogether (and that might not work).
Since there isn't an interview for the 1099-K, the only way you would have had a carry-over entry was if you had made a direct entry in this field last year. There isn't any reason I am aware of that would keep you from leaving that field blank this year.
The work-around (entering "$1") is the easiest way to get past the issue and won't affect your tax calculation in any noticeable way.
