static-maps use geocoding to locate addresses, you may see here that the given string didn't return a geocode-result: http://gmaps-samples-v3.googlecode.com/svn/trunk/geocoder/v3-geocoder-tool.html#q%3DZorlu%20Center%2C%20%2C%2034340%20Istanbul%2C%20TR
Google-Maps is able to locate the string, because it also integrates Places.
So what's wrong: the provided address currently isn't geocodable