I also ran into this issue. It showed that I owed a small penalty (<$50) for underpayment of tax, therefore, it wouldn't let me file electronically. However, when I tried to switch to printing the return, it kept me in a loop of need to "fix" M15 (underpayment calculation form), and not allowing me to file electronically. Finally, I adjusted the amount shown as an "error" which was my underpayment penalty amount, on M15, line 22, to zero. My assumption was then MN would catch the error and bill me for the small underpayment "miscalculation." So then I was able to file both the federal and state forms electronically. I then viewed the completed tax forms later and, it in fact, changed the underpayment penalty from $0 and instead showed the correct underpayment penalty and was filed correctly. So, in the end, the error message that caused all the problems was for naught. I was able to file Minnesota with the correct underpayment penalty even after I had changed it to an incorrect amount! This appears to be a bug in Turbo Tax.
