Okay, just tried out your setup with Tomcat 7 + FF8/IE9 and it is working over here. (with a trivial application)
I think the issue might be either in the compilation of the widgets or that you have a old cached widgetset in use.
First could you please check that you do have the following line in your widgetset module definition xml file (.gwt.xml):
<inherits name="fi.jasoft.uidlcompressor.UIDLCompressorWidgetset" />The vaadin plugin adds it automatically but if you are using a build script or another IDE you will need to do it manually. I probably should add that to the wiki as well…