Preview issue with UI Designer

Starting from, IIRC, IDEA 12.0.3, I'm seeing the following weird behavior when using Preview with a form designed in UI Designer:
That's how  the form I'm creating looks in IDEA:

But that's how it looks when running preview:



Notice the lack of text and icons in buttons. This same form, when displayed as part of the project in an actual application, looks just fine.

Not using resource for labels, simple text. It used to work just fine - now it doesn't work even for forms which used to work a couple of months ago.

Any help would be greatly appreciated.