This error appears in in some projects created with seam 2 when you try to create or edit a record in the web ui. It seems to be a bug.
You need to modify one line in either your seam-home/seam-gen/view/edit.page.xml.ftl or seam-home/seam-gen/view/edit.xhtml.ftl depending on your version of seam.
open up the file and change this line:
Then Re-Run ./seam generate and ./seam explode
Restart jboss and everything should be working
The final code chunk should look like this: