Ron
When I was on the phone with TT support, she initially suspected that the problem could be that the version I'm using (Deluxe) doesn't have the ability to handle 1099B forms. You may recall that several years ago, TT tried to drop that feature from the Deluxe version and force people who need it to upgrade to a more expensive package - they got a blowback over that one! So she upgraded me to the Premier version but that didn't solve the problem. Then, she had me delete the software entirely and reinstall it. Also didn't solve the problem.
I'm suspicious that the problem is that the downloaded data is corrupted, but I can't delete the data to repeat the download (there is a way to delete blocks of data using the 'forms' option, but when I try to use it, the software locks up.)
TT is supposed to be conducting an investigation, and I hope that they can find a solution. The only option that occurs to me is to delete the entire return and start over, and that would be painful since I was in the final steps prior to submission when this happened.
Normally, I input most of the data manually, and leave the 1099B download to the end because that data is subject to changes. But in the future, I think it might be more prudent to do the data download first so that if something goes wrong, throwing away the corrupted return and starting over would be less painful.