Please may I have your assistance with the following error I get when I process a Cube

I get a large number of the following error messages

A member with key '' was found in the fact table but was not found in the level 'Device Name' of the dimension 'device'.; Time:08/11/2004 12:32:52

When I view the device table the device name ('') exists hence I'm unsure why I get this error.

I've reprocess all my dimensions however this made no difference

The cube partition reached segment 34 before the errors began , could this be a limit with OLAP?

Any Ideas would be greatly appreciated