Car-Truck Worksheet - Depreciation Method error message "line 72 must be straight line if standard mileage was used in a prior year"

If you used actual expenses in first year you started using car for business then you have to use actual expenses for all future years. from pub 463.

Standard mileage rate not allowed. 

You can’t use the standard mileage rate if you:

Did the standard mileage rate create a larger expense than actual expenses so the system ran with standard mileage without you realizing it?

If it is a real glitch in the system, rather than what I mentioned above, you can always delete the asset and then enter the vehicle information in a new asset entry worksheet.

As was mentioned, on Line 24 you may want to click the box that 'forces' Actual Expenses over the Standard Mileage Rate.  You can also check that Line 15 says "no".

Another possibility is that sometimes the error messages are garbled and give the wrong reason for the error.  In the event that is the case, have you verified that the business percentage is over 50% (50% or less would require straight-line)?