Make sure you have administrator rights on your computer and TurboTax is running as administrator:
Right-click the TurboTax icon or setup icon and select Properties. In the Compatibility tab, select the Run this program as administrator box and select OK.
In the Control Panel under Internet Options, add https://*.intuit.com to Trusted Sites. Set security level to Medium.
Update your security software for firewall, virus, and spyware protection.
Make sure you're the only user on your computer running TurboTax. If you're not, switch users and sign out of TurboTax from the other account. If you can't do that, shut down your computer and try again. (Error: 70001)