Hola, ¿has probado de ponerle % en el ancho del objeto?
Código HTML:
Ver original<object width="100%" height="40" classid="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000" id="gsSong3016686451" name="gsSong3016686451"><param name="movie" value="http://grooveshark.com/songWidget.swf" /><param name="wmode" value="window" /><param name="allowScriptAccess" value="always" /><param name="flashvars" value="hostname=grooveshark.com&songID=30166864&style=metal&p=0" /><object type="application/x-shockwave-flash" data="http://grooveshark.com/songWidget.swf" width="100%" height="40"><param name="wmode" value="window" /><param name="allowScriptAccess" value="always" /><param name="flashvars" value="hostname=grooveshark.com&songID=30166864&style=metal&p=0" /><span><a href="http://grooveshark.com/search/song?q=Trivium%20Kirisute%20Gomen" title="Kirisute Gomen by Trivium on Grooveshark">Kirisute Gomen by Trivium on Grooveshark
</a></span></object></object>