Something happened and the program just added over $40,000 to my taxes due. How can I undue changes, or go back to a previous version?

[Vanessa A]

That sounds like you entered something without a decimal point or with too many zeros.  For instance, were you entering a W2 with $50,000.00 and instead entered $5,000,000.  

Go back and review all of your entries double checking decimal points and commas.