Update Issues explains problems you may have with updating and how to solve these issues. TaxCut suggests disabling your firewall if it appears to be interfering with TaxCut updating. Before disabling the firewall, check to see if your firewall has a URL exceptions feature where you would add http://www.taxcut.com/updates to the exception list.
By adding an exception to your firewall, you do not need to disable it and expose your computer to anything nasty on the Internet while downloading updates. You won't have to remember to enable your firewall after the download, either. Check your firewall software Help to see if you can create an exception and how to do it.
If this video does not help you with an update error, check out TaxCut's Online help for update errors.