1) Create new Seam or JSF project.
2) See flash movie to reproduce this bug.

I was able to reproduce first test case when renamed .jsp, .xhtml., html., jspx to any other web format (change current extension to another extension from the same row)

Second testcase was being reproduced when tried to rename .jsp, .xhtml., html., jspx to any other random format (txt, gig, jag and so on)