panels arguments 404

Hello,

I'm having a weird problem with panels arguments passed as a string context.

ctools-1.3
panels-3.3

I need to build a page which takes an optional date formatted string and passes it to a view pane powered by the Calendar module. I've build a panel page which takes 1 argument: /programs/!date where !date is my optional argument. Then, I configured the argument to be a string context since none of the other options were really fitting. Finally, I added the calendar view to the content lay-out and configured it to pass the panel argument to the view.