On Mac with JDK 7u4 it is not possible to run a Java/JavaFX project using WebStart technology. Run fails because webstart executable is not found.
The issue is caused by a problem outside NetBeans. JDK 7u4 indeed does not support WebStart technology. However, WebStart support should appear in next upcoming Mac JDK 7 updates.
If a NetBeans Java/JavaFX project is set to run as WebStart on Mac JDK 7u4 in NetBeans 7.1 or 7.1.1, the run operation simply fails. NetBeans 7.1.2 and 7.2 on Mac JDK 7u4 additionally write out a message explaining that WebStart is not supported on Mac JDK 7u4. The build process is not affected and produces WebStart related artifacts (JNLP file) as expected.
Remark: MacJDK7u4 detection and warning has been added to FX build scripts as part of issue 208798:
and to SE WebStart script in changeset:
Integrated into 'main-golden', will be available in build *201203240400* on http://bits.netbeans.org/dev/nightly/ (upload may still be in progress)
User: Petr Somol <firstname.lastname@example.org>
Log: #209915 added warning to SE WebStart scripts about missing support in MacJDK7u4