I just loaded up the latest dlls and it seems that the radupload is fixed width at 430 and the width attribute in the tag does nothing. It use to display fine at width="100%" and now its stuck at 430px. Did something change?
Have you tried using style="width:100%" ? That just worked fine for me with a few skins... let me know if that works. I seem to find that a lot of the controls respond better to css styling for sizing than using properties.