I am trying to show a \'Post to Your Wall\' feed dialog with the following code in a facebook iframe app:
I know this is a bit old, but I stumbled across this page when trying to solve this problem for myself and none of the answers here worked for me.
For the benefit of anyone else who has this problem, this was happening for me because I was trying to call the dialog on page load. Moving it to a user triggered event (such as a click) resolved it for me.