I am having the same issues, and it doesn't exactly seem to be temporary (it has lasted for the past few days, and my other apps that use dropbox work well (1Writer, WordEver, PlainText). I really love the design and concept of this app, but this issue hinders me from using this as my primary app choice.
Perhaps there might've been a recent change in Dropbox's API, or some sort of change in response formats that's causing the app to misinterpret something as 500?
Thank you for your efforts on such a wonderful tool!