iPhone mapview will only update when in wifi

I have a little application in progress. One of my current problems is: it seems that the MapView will only load map data when I am in wifi range (when e.g. zooming in). When only 3G/2G is available, it displays the tiles already cached but will not load new ones. It seems to b开发者_开发百科e no problem with the general setup of my iPhone: the Maps application works nicley.

Any ideas?

... well, looks like I was indeed too impatient. Sometimes, it takes a lot of time until the maps starts loading.