EXECUTE: Create New Seam 1.2 WAR project.
EXECUTE: Open pages.xml, go to Graphical tab.
EXECUTE: Click on "Add Exception" button. Draw box, input name here, press Enter.
ASSERT: Exception appears in view.
EXECUTE: Right click on it, select Properties.
EXECUTE: Click on small browse button in Class field.
EXECUTE: Select any class - for example javax > accessibility > Accessible, press Ok.
FAILURE: Unhandled event loop exception thrown in Error log. Class didn't change.

Log attached.

Possibly related to JBIDE-3934