As a follow-up to my original post, I will add that I waited online for 45 minutes to actually talk to a TT representative who, despite her persistence and interest in solving the problem, was unable to make the error message go away. I was able to manually input the correct dates into the form using the Forms portion of the software, but the error message persisted. Since I didn't plan to e-file my state return, and since this error only affected that one part of the state return, and since the printed copies I was going to mail in did not include this particular form, I chose to ignore the error message and proceed with filing as is. This came with the consensus of the TT rep, who could not make the error message go away, but said she would note this problem as an issue which they needed to address.
I hope this helps anyone else who has converted a traditional IRA to a Roth in the state of Michigan. Good luck!
