I had a working Wxs file I had been building using V0.6.1762.  I need to add a firewall exception when installing onto a Vista machine.  In order to do so I need to alter the schema line.
Normally this reads
<Wix xmlns="http://schemas.microsoft.com/wix/2006/wi">
but it now reads
<Wix xmlns="http://schemas.microsoft.com/wix/2006/wi" xmlns:fire="http://schemas.microsoft.com/wix/FirewallExtension">
While WixEdit opens the file without any problems, the moment you try and open the build menu, you get an error box appear.  The menu never appears so I am unable to build the install. 
The error states
Error Message: Namespace prefix "firewall" is not defined.
If I build by running Candle and light from the command prompt, the file builds the MSI without any errors.
I have checked the docs directory and firewall.xsd is there and WixEdit setup points to the correct folder.
What did I miss?

Chris Lord