hmm, not certain why that is. I just tried to log back into your work space, but was unable (and now may be locked out). The application is quite large, but try logging in as fedsuper/sharkbait and then go to PARTICIPANTS--> select a name then hit EDIT. Page 311 will appear.
if not, let me know and I will just import the page w/out authorization.
What you could do is change the button to "defined by Dynamic Action" and basically you can call a js function and pass in the url 'f?p=&APP_ID.:85:&SESSION.::::P85_PARTICIPANT_ID:&P311_PARTICIPANT_ID.'