I had the same issue and found the solution posted here in QlikCommunity (don't remember where though).
- Go into the Chart Properties and select the Colors tab
- In the Frame Background section, edit the Dynamic Image expression
- The last line will have: '&key='&gmap_key & '.jpg'
- Put an & in front of .jpg so it looks like: '&key='&gmap_key & '&.jpg'
Hope this helps.
Remember that the free use of the Google Maps API in an internal non-browser application is strictly forbidden by the terms of service. http://code.google.com/intl/de/apis/maps/terms.html.
I would highly recommend the use of OpenStreetmaps for that kind of Applications!