Sometimes when using NetBeans 7.1 valid, previously working JavaFX applications fail to start.

The application is clean-built properly, with no errors. When trying to start it NetBeans initiates the run and then indicates that the application is running. However, the window doesn't show up (despite having stage.show() at the end of overriden start() method). Other times, the same application starts up perfectly. Sometimes, the same application can't start for several times in succession, and then starts up perfectly.

JavaFX process can be observed in Task Manager, but jstack cannot use its PID to retrieve any information (jstack freezes).

Reproducible with NetBeans 7.1 RC2 (http://dlc.sun.com.edgesuite.net/netbeans/7.1/rc2/start.html?platform=windows&lang=ru&option=javase)

JDK info:
java version "1.7.0_01"
Java(TM) SE Runtime Environment (build 1.7.0_01-b08)
Java HotSpot(TM) 64-Bit Server VM (build 21.1-b02, mixed mode)

JavaFX: 2.1 b06 (however, reproducible with b05 also).

OS info: Win7 64 bit