R&B sensation Maxwell announced Saturday that he has been forced to cancel all of his upcoming tour dates after suffering from vocal problems including swelling and hemorrhaging.  The singer had a total of six scheduled shows coming up, but doctors have advised him to cancel the appearances and get rest in the interest of making a full recovery.  The singer did vow to make up for the dates after the release of his fifth album later this year.  Maxwell's last album, released in July 2009, earned the singer a pair of Grammy Awards and has sold more than a million copies in the US alone.