I'm seeing some weird issues with sprites when using scaling, either manually via xScale/yScale or the dynamic content scaling for different devices.
I've seen issues like this before but it was for when you transition the sprites, in Lime I fixed this by making sure the x and y positions were always rounded so I have a feeling this issue may be fixed in a similar way.
When I increase the scale of the display group that holds the sprites by .1 ( tap the screen in the demo ) the actual xScale and yScale changes to something like 1.1000014838 and whenever I try to round it it doesn't make a difference, the scale always goes back to an unrounded value. This means that this may not even be the fix as I can't prove it will work.
I have created a simple demo to show this off, and I have made it so that you can switch to rectangles, images or sprites and the issue is only visible when using spritesheets. Uploaded to here - http://dl.dropbox.com/u/571145/SpriteScalingIssue.zip