Of late I have noticed that all thumbnails of images I upload via the Flash uploader or the browser method are cropped square. Clicking on the thumbnail takes you to the properly proportioned image, but it can still make for some odd-looking posts where the thumbnails have important information cropped out!
Looking back through my posts I note that this hasn't always been the case and looks like it might have crept in around 2.5.x (I am using 2.6.1).
A quick search through the forums found a similar post, but there were no replies, hence the new one.
So, to summarise, how do I revert to thumbnails that are miniature versions of the original rather than square and/or cropped?