An unknown item is declared as the root...

whenever start new project, error.

"an unknown item declared root
of mxml document. switch source mode correct it"

and here's exact source fb4 builds me.

<?xml version="1.0" encoding="utf-8"?>
<application xmlns:fx="http://ns.adobe.com/mxml/2009"
                xmlns:s="library://ns.adobe.com/flex/spark"
                xmlns:mx="library://ns.adobe.com/flex/mx">
     <fx:declarations>
          <!-- place non-visual elements (e.g., services, value objects) here -->
     </fx:declarations>
</application>


i looked @ other project working on, , it's working great, instead of <application> it's <s:windowedapplication>

how can fix can work on new projects?

try flash builder forum.  generated code invalid.  missing

some namespaces.

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