Steamtrain- I'm marking your answer as best because, although the TT rep led me thru the way to fix this, your solution worked as well. (I had TT desktop installed on 2 computers in the chance that is was a computer-specific issue.) I was able to complete my return over the last two days once the rep got me to a solution, but I just now fired up the other computer, went to the SSA-1099 form page, double-clicked, and deleted the lines on the supporting, linked doc. The problem is fixed there as well now.
