In Internet Explorer 6 whenever I upload images, they only render as thumbnails, even when I set it to 'Use Original' via the dropdown in the Browse All panel.
I can get the image to show up original size ony by a very contorted method - by clicking on the little Image Edit icon in the text editor and clicking Update. Then it resizes.
You are also able to resize in the edit panel using the handles, but there is no way to constrain the image to its correct proportions, therefore it is difficult not to squash/stretch.
In Firefox, the original size is placed in the editing panel correctly.
This caused great embarrassment at a public demo where I had to use Internet Explorer 6 and did not realise this was an issue.
Other posts suggest that others have identified this problem: