(Updated Monday, July 25th, 2011) We have identified a bug with iTeleport v5.1.0 that causes a crash when connecting using Mac authentication to Screen Sharing, when the username or password contain non-English characters.  The update should be available within a week's time.  In the meantime, a temporary workaround is to use English characters — we're sorry for the inconvenience.

(Updated Wednesday, July 27th, 2011) This has been fixed in iTeleport v5.1.1.