craftersuniversity on "[Plugin: Invite Anyone] Missing error page"

When i try and invite an user who´s email address is already registered on my site, i get a blank page. What i would like is a descriptive error messages stating that this email address is already registered. I do however see the error message in the address bar, but the page itself is blank. Does anyone know what the problem is?

Text in address bar:

http://craftersu.com/members/crafters-university/invite-anyone/invite-new-members?error_message=%3Cstrong%3Einfo%40craftersu.com%3C%2Fstrong%3E+is+already+a+registered+user+of+the+site.%3Cbr+%2F%3E&error_emails%5B0%5D=info%40craftersu.com&subject=An+invitation+to+join+the+Crafters+University+community.&message=You+have+been+invited+by+Crafters-University+to+join+the+Crafters+University+community.Visit+Crafters-University%5C%27s+profile+at+http%3A%2F%2FCraftersU.com%2Fmembers%2Fcrafters-university%2F.&groups

http://wordpress.org/plugins/invite-anyone/