AWTUtilities.setWindowOpaque is causing some text painting issues

Question

I am attempting to create an opaque JWindow with antialiased rounded corners. In doing so, I call the method:

AWTUtilities.setWindowOpaque(this, false);

And use a custom JPanel which paints the actual rounded corners.

Within the window, I have a JList. Whenever setWindowOpaque is set to false, the text within the JList becomes "distorted" slightly (i.e. it is still readable but it is noticable).

I'm trying to figure out exactly how to resolve this issue. It is possible to set the window shape itself using AWTUtilities.setWindowShape but this results in a non-antialiased shape.

For the record, I'm testing this on a Windows 7 machine with JDK 1.6 update 20.