In my case also, the import succeeded with a warning like, "Wow, you have a lot of 1099-B transactions; this is going to make TurboTax really slow. Press continue to hate TurboTax or cancel to go to jail for not doing your taxes."
I decided to hate TurboTax and stay out of jail, and what I found is that when I went to update any 1099-B information at all (including from other brokers) the TT program appeared to hang. It hung for a half hour or more, and I finally force-quit it. But on a lark some time later, I repeated the process and this time I just let it run for several hours. And lo and behold, eventually it un-hung itself and started working. Subsequently, some steps would be rather slow, but not in the extreme like I had experienced. If your luck is the same as mine, you'll be able to leave it seemingly hung once for a long time, and after that it will be usable (albeit slow).
