OK, someone mentioned cookies and that sounded like a good suggestion. Cleaned out all the cookies in my Safari browser and now am able to access the Target sites.

So if you have this problem... throw out the cookies!!!

I get exactly the same behavior. It worked fine the first session after I signed up. Since that I get these error messages any time I try to access any Target content. I am running Safari browser on a MacBook Pro. I do not get this behavior on any other site.