We had this problem and after trying pretty much everything mentioned in this thread with support, we asked for permission to install on a different machine in the house. Exported the return, imported to the new install and it filed with no issue.
On the original machine, there was no rhyme or reason to the failure, but it was permanent. Reinstalling TT had no effect, it failed in exactly the same place with the same error. But it was not the first return filed on that machine this year, I think that says something about the cause. The return successfully filed before the errors started was for the same state, both were simple. Makes no sense.
