This problem specifically affects widgets that have not yet been voted on. When the widget is empty, the description text is blank and the description is given a class of "fivestar-summary-". This should be populated with "No votes yet." and have a class that matches the configuration settings for that node type.
This problem seems to be caused by using NULL as the default value for votes if they're not found. When theme_fivestar_summary() is called, it specifically differentiates between NULL and a 0 value. However if we're passing in a value of NULL when a node hasn't received any votes, this results in all the parameters being NULL and no text is generated at all. We should pass in 0 when a user hasn't voted.