New Post: XMLBasedSiteBackup gives 404 Page does not exist

For no apparent reason my XmlBasedSiteBackup package has stopped working.
In the admin control panel I go to System, select Xml-based site backup, then click Open, and the frame displays:-
_Server Error -
404 - File or directory not found.
The resource you are looking for might have been removed, had its name changed, or is temporarily unavailable.
_
As far as I can see I have changed nothing. This was working a week ago.
I have tried:-

• different browsers
• cleared the browser cache
• done a Restart Server in the admin control panel
• created, visited home page, then removed app_offline.htm to make IIS clear and restart the app
• used IIS to stop/restart the website and recycle the app pool
  

If I view the frame info it is trying to show the following URL:-
http://www.sarahpayne.co.uk/Composite/InstalledPackages/content/views/Composite.Tools.XmlBasedSiteBackup/XmlBasedSiteBackup.aspx

Inspecting this location on the server with file manager shows both the XmlBasedSiteBackup.aspx and its aspx.cs files exist.

Also if I try that URL directly in the browser address bar it gives 404 error.

Firebug shows the control panel doing POST ConsoleMessageQueueServices.asmx a few times and POST TreeServices.asmx ok, then shows GET XmlBasedSiteBackup.aspx 404 Not Found.

I have also uninstalled the XmlBasedSiteBackup package, then re-installed it again.
Everything else in the website and the control panel looks like it works correctly.
The server log does not give any error messages.
My local development copy works fine.
Why oh why?