【Netbeans】Java桌面应用程序如何正确使用Proguard进行混淆

经测试，运行混淆过的console程序无误，但是运行GUI程序则会统一报如下错误：
程序为未写任何代码直接新建的工程。IDE为7.0.1，ProGuard为最新版，记得是4.7。哪位朋友有思路，请不吝赐教，非常感谢！
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C:\Documents and Settings\Administrator>java -jar "C:\Documents and Settings\Adm
inistrator\My Documents\NetBeansProjects\PGTest\dist\PGTest_output.jar"
2012-4-1 15:12:35 org.jdesktop.application.Application$1 run
严重: Application class pgtest.PGTestApp failed to launch
java.lang.NullPointerException
        at pgtest.b.<init>(Unknown Source)
        at pgtest.PGTestApp.startup(Unknown Source)
        at org.jdesktop.application.Application$1.run(Application.java:171)
        at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:597)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThre
ad.java:269)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.
java:184)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThre
ad.java:174)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)        at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)
Exception in thread "AWT-EventQueue-0" java.lang.Error: Application class pgtest
.PGTestApp failed to launch
        at org.jdesktop.application.Application$1.run(Application.java:177)
        at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:597)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThre
ad.java:269)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.
java:184)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThre
ad.java:174)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
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