Web Service responding 'Unauthorized'

I'm trying to move a Web-based app from my local testing server to a remote host.

The app is developed in PHP using a PHP version of the API for MapPoint (which is brilliant, by the way) which I've downloaded from PHP classes.

It works well on my testing server, but try the same code on the remote host and I'm getting an 'Unauthorized' response from MapPoint.

Any ideas what may be causing this?

Thanks

Ensure the developer account credentials are supplied to the Web Service