This type of error is come due ur .xap file contain a space like
u should remove these space between the name u render it into the iframe of <object> tag
and ur layout structure size of Silverlight control like width and height Should be the same as the webpart size u declare in that page.
When u run any silverlight control or application it render it into the iframe with 100% height and width So if ur Silverlight control size is greater than the webpart size u got only some portion display on ur page
So specify only that that much height and width to ur silverlight control u need further
i am sure about it, it works well