Part of the fix for 6432397 was to get XPStyle.getSkin to return 'null' if PART is not defined in the current theme. That has caused some problems:
6467366 REGESSION: JFileChooser displays garbage as Applet using WinXP LAF
6470308 Switching between "Windows and button" style on XP, color schemes on Vista is throwing an NPE.
While these problmes have always been there after the change for XPSteyl.getSkin the manifestation got worse.
I suggest to revert XPStyle.getSkin to not return null.