I am using Twenty 10.
I have assigned an image as a header.
I have a fixed page as the landing page.
I assign featured images to posts so that the thumbnails in your lovely plugin will be seen.
If I am on my landing page all is well. Header image and thumbnails looking as they should.
If I click on the Blog link, all is well, header and thumbnails looking good.
If I click next or previous post, all is well, header and thumbnails looking good.
But … if I click on the thumbnails to directly click to the associated post, the thumbnail image bumps the header image.
I have tracked this down to being the result of the featured image being large: 800 - 1024 pixels wide. When I changed the featured image to 300 pixels wide, all is happy and well. When I click on the image to navigate to the post, the header is as is should be.
It was convenient to just assign an image that I already uploaded as the featured image, not a big hardship to create a separate image for the thumbnail, but in case there is an easy fix...or in case someone else has seen this and wasn't sure how to fix it.
This problem happens for WP versions 3.4.2 and 3.5.1.
I am using MacOS 10.7.5
Safari is browser of choice and is v5.1.7.
My website is here, if it's helpful to see how I laid things out. The problem, however, is no longer a problem since I corrected the featured image sizes.