Use your developer toolbar (Chrome) and inspect the image. If you don't see anything wrong with the image, work up the DOM until you see the problem. Check their widths, heights, paddings, margins, and "top" and "left" CSS attributes.
This element <div class="avatar-image-container vcard">
has max-height: 36px
which is too small.
The image element itself has width and height attributes of 35x35 even though the image is 45x45.