It's a glitch.
Besides, only the brave transfer clients this early. Intuit always leaves landmines in the software that explode when it is time to actually prepare returns. Transfer a couple of clients now if you want to play with the software, otherwise be safe and wait until January.
I would wait until January to transfer over clients. Create a dummy client for now to play around in the software. The updates can really mess things up between now and then.
Actually same thing just happened to me.... I was only brave enough to transfer my own file of course.
I called and had intuit SmartLook on my PC. Unfortunately, the fix was a bit complex all things considered.
Steps she gave me and when applied solved issue.
1. Go to File and click NEW FILE.
2. Once the NEW one opens go to FILE and Choose TRANSFER, select the return that had the error message.
3.Once transfer occurs just go to HOMEBASE and when prompted if you want to save YES!!.
It totally worked and since I knew exactly which return it was , it was quick. She did ask me if this happened to multiple or a single file..... Guessing waiting until JAN not the end of the world.