NotDone: I used to run across that problem when I logged in to file and filled out the form there. It kept timing me out - very frustrating. Not sure if that is your issue or not, but I started saving a template of the form, working it, then logging in to just file it.
To Do: I got an error about my PIN not working once, and called the tech support line. He worked with me for about an hour, and it turned out that the attachment file I had named had a character it didn't like. I can't remember what the character was, maybe a hyphen, or number sign. The error message was completely unrelated to the true error. Even the helpdesk was baffled. Do you have an attachment to your file?