Can't enable Java Web Start for Java Project created with existing sources

NetBeans build:
NetBeans IDE 5.0 Beta Build200509261930
JNLP Plug-in build:
08-Oct-2005 16:18:37

Prepare:Install the jnlp plug-in for netbeans

Steps :
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1. Create a new Java Application with existing sources
Select "Java Project with Existing Sources" when create new projects
2. Select this application in Projects View , right click mouse and invoke "Enable Java Web Start" from contextual menu

The jnlp file can't be created on such project , and the application can't Run or Deploy with Java Web Start.