Design mode not working for Flex 4 project

Question

I'm trying to port a small Flex 3 AIR project to Flex 4 (Gumbo). Things are working quite fine. I can run and debug the application. But for some reason I can't use the design mode of my WindowedApplication. The head of the MXML file looks like so:

<?xml version="1.0" encoding="utf-8"?>
<WindowedApplication xmlns="http://ns.adobe.com/mxml/2009"
        xmlns:mx="http://ns.adobe.com/mxml/2009"
...

I get an error saying that the root node is not recognized.

Anyone else got this to work in Gumbo? Any pointers?

Answer 1

Looks like you've encountered a known bug