OK. Sorry. I did not see those instructions on the url you gave, but I did figure out that this is a theme issue. Apparently the upgrade broke one of available navigation menus available through the theme.
I know the upgrade broke it because no other of my installations of this same theme have the problem and none of them have been upgraded.
I have turned off that navigation menu on one site for now so the problem is not an issue except that I can no longer use that menu, but hey I am sure it will all work out. :)
The theme is Suffusion and I will be notifying the developer of the issue.
Thanks for your time,
BTW: should be marked as resolved here? IDK