I have a template with delivery option = email.  I have a button on the Contact that generates the form.  After the form generates and I click to continue, it forces me to logon (even though I am already logged on).  It does this for all user profiles.  (and then later salesforce makes me log out of all other windows I had open, even though they were logged into using the same logon credentials).  This does NOT happen if I run the form directly from Nintex test button.  It only happens when i run it from the button i put on the Contact.  This is what the contact button url looks like (123 is the contact id, and 456 is the id of the email delivery option): 

/apex/loop__looplus?&eid={!Contact.Id}&ddpIds=123&deploy=456&autorun=true

(note: i have tried removing the autorun option and this does not fix the problem)

Any ideas what is causing this? the problem only applies to the email delivery option (download works fine)