I had the exact same error on one of our processes and could not find the formatting issue in the excel file. My fix was to use the excel read range activity in stead of the workbook read range activity and the error went away. So if you have excel on the machine that you are running on then you can just switch to using the excel activities and that should work.
I had the same error. Fixed it using the advice below. My problem was an excel read range that stopped working. I replaced it with an excel application scope containing the newer excel read range and it works fine now.