First, make sure you check for, and download / install any Windows updates. There were some .NET updates in the last two weeks. Reboot your computer even of you don't find any. And try again.
Still a no-go?
Go thru this to see if anything there helps:
https://ttlc.intuit.com/community/bugs-and-error-messages/help/error-1603-a-fatal-error-occurred-dur...
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After that, it's off to Customer Support for help on the phone:
https://ttlc.intuit.com/community/using-turbotax/help/what-is-the-turbotax-phone-number/00/25632
____________*Answers are correct to the best of my knowledge when posted, but should not be considered to be legal or official tax advice.*
