Happened to me on mobilepic.twitter.com/k1UWKZ3WMw
You can add location information to your Tweets, such as your city or precise location, from the web and via third-party applications. You always have the option to delete your Tweet location history. Learn more
Hi Dan, does this happen across devices? Also, you could try clearing the cache and cookies and let us know if this helps!
Twitter may be over capacity or experiencing a momentary hiccup. Try again or visit Twitter Status for more information.