When I use "Set Password on Multisite Blog Creation" with my multisite blog it breaks the validation on Pro Sites Sign Up. If I fill out all the fields it processes the signup, but doesn't move to the "payment" screen. If I refresh the page, the payment screen then shows.
Further investigation shows the error comes from the checkout.js response:
Setup your site<\/h2>\n\n\t\t\n\t\t\n\t\t\n\n\nUsername:<\/label>That username is currently reserved but may be available in a couple of days.<\/p>(Must be at least 4 characters, letters and numbers only.)<\/div>Email Address:<\/label>That email address has already been used. Please check your inbox for an activation email. It will become available in a couple of days if you do nothing.<\/p>We send your registration email to this address. (Double-check your email address before continuing.)<\/div>\n\t\n\t\n\t\tFirst name<\/label>\n\t<\/p>\n\t\n\t\tLast name<\/label>\n\t<\/p>\n\t\t\n\n\n
... and a whole bunch more......
I have deactivated all plugins and its still throwing this error. When I deactivate "Set Password on Multisite Blog Creation" the sign up process works fine.