I've got two issues with big issues: When using full size images, the image description lacks padding on top and the background is not wide enough. mid-size images are fine.

This pretty much sums it up visually: http://s275144270.online.de/testblog/

My fault? Atahualpa bug?

You need to add

	max-width: 96%;		/* 	resize images in the main column if needed.
							97% so images with padding and border don't touch
							the right sidebar while being resized. Change this 
							to 100% if you want, if your images
							don't have padding and a border */
	width: auto 100%;

to the .post img.size-full that you have in the CSS Inserts. You may want to do some adjusting of the numbers

Thank you!