strangerstudios/paid-memberships-pro — pull request #56 by inator (2013-08-13 01:23:06+00:00)
Title: Fixed issue with bad invoice info on zero due reoccuring checkout.

Have a look at http://wordpress.org/support/topic/confirmation-page-after-purchase-does-not-display-invoice-properly?replies=5#post-4527090

I think this should do the trick.