I have a JProgressBar set with Indeterminate state and added to a JPanel. the JPanel is added to the center of the frame. I have 2 buttons one on the south and other on the east side of the frame. Now clicking one of the buttons change the orientation of the progress bar from vertical to horizontal and vice versa. After changing the orientation, try resizing the frame inward either horizontally or vertically depending on the orientation of the progress bar. You will notice that a portion of the progress bar appears on top of the button and remains unpainted.

I reproduced this on WinXP with 6u10-b11/12 using the attached test. This is not reproducible with any of the other look and feels such as Metal and Windows.

To reproduce the bug, run the attached test with Nimbus Look And Feel. Click on 'Change' button. Resize the JFrame inward and see if the progress bar overlaps the button.