Have you turned on the 'Show alert on not found' option? It might be that it is not getting any addresses or they are unclear.
This option is on, thanks Robert. It definitely finds the address because when I click on the address (I'm using 2 panes, with the google map overview pane listening to the address list pane), it pans to the correct address (I've set pan to context on). Marker attribute is set to CustomerName, which is definitely populated (are there any restrictions on size of this ?).
thanks & regards Paul