Android AdMob problem showing graphics

I'm facing weird problem while implementing AdMob into my application. The problem is that ads are not showing at all or if they will (sometimes, but it is rather rare), the left image on it still doesn't (there is question mark like on web page when can't open a picture).

I'm using the newest jar file from AdMob site. Any ideas, how to make them working properly?

PS. It ha开发者_如何学JAVAppens on real device, on emulator everything is ok.