Man, that's kind of crap. I had a similar experience lately--I applied for some museum studies internships only to find after I'd left some boxes blank on their online app to fill in later (personal statements and the like) that you couldn't go back and edit the boxes.

Absolutely the worst online application I've ever seen.

Turned out that once you hit the "application complete!" button, it did give you the option to go back and edit things, so I was not so completely screwed, but it gave me more than a couple of days of angry distress.