Problem comes from this.transformNodeToString(xmlNode) function in Util.js .
With TabbedContent widget , this function tries to transform an XMLElment to a string and IE doesn't permit it
With others Widget , it's an XMLDocument who is transform to a string.
This bug occurs since Sarissa has been updated ( I think but I'm not sure) ,
so probably a patch could be applied to sarissa (Jean-Sebastien is the most appropriate person to do that).
Waiting this patch, I commit a quick hack in this function who transform xmlNode to an XMLDocument when browser is IE