On the Windows 7 we have 3 of them failing; on OS X, one.
For Windows, robot.waitForIdle() apparently is not enough and some plain delay on the main thread is necessary before getting location on the screen via Util. On OS X 10.10, test 8145060/TestJInternalFrameMinimize.java just says "Test failed": perhaps it is a product bug.

RULE "javax/swing/JInternalFrame/6288609/TestJInternalFrameDispose.java" Exception java.awt.IllegalComponentStateException: component must be showing on the screen to determine its location

RULE "javax/swing/JInternalFrame/8145060/TestJInternalFrameMinimize.java" Exception java.awt.IllegalComponentStateException: component must be showing on the screen to determine its location
RULE "javax/swing/JInternalFrame/8145060/TestJInternalFrameMinimize.java" Exception java.lang.RuntimeException: Test Failed

RULE "javax/swing/JInternalFrame/8145896/TestJInternalFrameMaximize.java" Exception java.awt.IllegalComponentStateException: component must be showing on the screen to determine its location