All my project have a failure in the design mode. Only the source code mode is available.
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All my project have a failure in the design mode. Only the source code mode is available.
Then it appears you're in trouble. My guess is that a set up file used by NetBeans has become corrupted, but it's impossible to know for sure based on what you're telling us. This is yet another reason to do your Swing coding by hand and to not rely on potentially unreliable code-generation software.
Did you change anything since last time like you created a JFrame on design mode then on source code you change JFrame to JDialog, something like that?