Oh, no problem.
I see in your page several warnings in the console. Did you manage to solve/remove them all for your tests?
So you're saying that you went back to just WordPress and s2Member in your test, no other plugin or theme than the default?
This is something I only see when there's a JS conflict by a plugin or theme.
If you could, for a new test, create a clean installation of WP in a subdirectory, and add only s2Member, and try to reproduce the problem there.
I look forward to your update.