BPC querying wrong source

In 7.5 when you create anew application BPC generates a multiprovider and a cube. All BPC querys are directed to the multiprovider and so reach the cube indirectly. This gives you the ability to add other cubes to the same multiprovider.

We have a situation where BPC is not querying the multiprovider. An examination of generated MDX clearly shows it is querying the underlying cube.

Can anyone advise how this situation could have arisen?

Thanks

Cliff