So I just got dumped off of a Chat support with these instructions but it still didn't work:
Open Finder and click on the Go menu in the Apple Menu Bar.
2. Hold down the Option key and choose Library
3. Open the Cookies folder and locate these files
com.apple.appstore.cookies
cookies.binarycookies
4. Go ahead and move those files to your desktop, then restart the Mac
If the issue is resolved with this, those files can be deleted by moving them to the Trash. If the issue continues, we may want to explore alternative resolution steps.
I was also told to make sure I had the latest iTunes version which is 11.1.3... I have only 11.1... so tried to do that and yet another fatal error message. I couldn't reestablish contact once I restarted (of course) so I don't know what the alternative steps are... sorry...
So maybe this will work for someone else?