I have noticed that I get the same error, but only when I have logged in to see work with my teams. If I want to see another league's drafts, I make sure to do it before logging in to manage my own team. It works 100% of the time, so I rarely login to look at PB, unless I'm playing a home game or making roster adjustments between Tue-Thurs. In short, to look at old drafts from other launch leagues, do that first, and then goto your own LL and login to edit your draft list.

Jon