Many people have emailed me, as well as a thread on the forums, about their map not rendering properly on their page.   This hasn't been a big deal in many cases because it is the marker data that triggers the problem and can easily be resolved.   Here are just a few examples of what maybe the issue:

1. The Latitude and Longitude are entered in degrees, minutes and seconds format (DDD MM'SSS").  GMaps only supports DECIMAL format like 38.23292 and 90.23323. 
   
2. There is a single quote within the title and/or description of the marker.   (This can be resolved by escaping the single quote)
3. A  more recent issue that has been reported is when using themes that try to fix the IE6/PNG issue.  In this case, you will possibly see the map boundry and a marker or two, but no map image.  One quick solution to this is to comment out the line using the libary to resolve the IE6/PNG issue; however, that may cause an adverse effect on other areas of your site.