Because of the large changes in the MXML attributes from Flex 2 to Flex 3, it wasn't possible for me to spend enough time changing the [node:1344] to support the new version.
Fortunately, there is no need for me to do so because the XSD4MXML project has one for download, plus source code to generate it yourself from Adobe's own source code.
The application is powered by a file called mxml-manifest.xml which you can find in the frameworks sub-directory of the SDK. One for Flex 3 is included in the downloadable code for xsd4mxml.
You should be able to use the same file from the Flex 2 SDK to produce an up to date and accurate version of my file too.
Using this file allows a (free) generic XML editor to verify your MXML code. If you don't have Flex Builder, this will be great news for you.