"Starting IIS Express...

Report ListenerChannel stopped due to failure; ProtocolId:http,ListenerChannelId:0

HostableWebCore activation failed.

Unable to start iisexpress.

The interface is unknown.

For more information about the error, run iisexpress.exe with the tracing switch enabled."

Try to un-install and re-install IIS Express? if you haven't tried, try to re-install and see if this problem is solved.

If re-installation of IIS Express doesn't solve your problem, then following is a workaround.

1. open applicationhost.config located in user profile directory (%userprofile%\Documents\IISExpress\config\applicationhost.config)

2. Find following two entries in the above config file and remove them (or comment them)

<add name="HttpLoggingModule" image="%IIS_BIN%\loghttp.dll" />
<add name="HttpLoggingModule" lockItem="true" />

3. Now start IIS Express from command line. If this works, you can open WebMatrix and 'Start' a site

Note that with this workaround you don't see http log files, but IIS Express should just work fine.