I too had similar problems with just a yellow box showing up, but my Adsense publisher ID was missing numbers off the end. I entered it properly (without the "pub-" part), waited 5 minutes, and ads are now showing successfully.
The problem now, is that they are being cut off. For example: http://www.gohomeyouaredrunk.com/yummy-cat-is-yum/ underneath the picture, there is a bit of the yellow box still showing and one of the ads is hidden. Do you know if this has happened before, and if I can fix it?