Boris,
I added a new Matisse form to my project, added a new JPanel to the form and then added a JCheckBox to the panel. Next, I right clicked on the check box and selected Edit Text and entered a random name. Now when I check the source, it populates the text using the .setText() method.
Are you referring to some other condition?
You should try switching to a new workspace, creating a new project and test this again.