Avex video converter to iphone "output error"

[mrz0gz]

I'm using this program called "Avex" which helps me convert media files mp4, avi....etc to my iphone. i grabbed the file (avi ) and loaded it onto avex program it recognize the file, and when i go to click on convert i get this error " could not find suitable output format". I've tired different files like avi, mp4 and still i get the same error. I'm not too sure how to fix this problem, anyone have any ideas ? thanks