Strange. The URL of that page looks to be a permissions page (similar to when you login to Sourcecoast the first time, or any Facebook App). It's normal to have to grant the Facebook Developer App permission. It's strange that it's not working though, and that's not something we can test right now since we've already approved it.
We are using Chrome. However, that popup should work in IE, Safari and Firefox as well. I'd recommend trying them all and see what happens.
You may also want to try this link, which is a direct link to the app creation process. It may help kickstart things:
developers.facebook.com/setup
Definitely keep us posted, but really not sure what's going on. Unfortunately, there's not much we can do other than some random suggestions which may or may not work or telling you to simply wait. I just searched around for bug-reports similar to this on Facebook. The best I could find (opened recently at least) was:
developers.facebook.com/bugs/399503013424480
Did you verify your account yet? Not sure if that's after you approve the app or before it (Thought it was after, so you may just not have gotten there yet). Either way, read it please and let us know if you started that process or not.
Thanks,
Alex