Janne,
I made an install of 1.2 beta last night and noticed that when I insert an image into the editor using IE6, it is not sizing correctly. Image appears with only bounding boxes (pic 1). You can grab a box and stretch the image, but have to guess on aspect ratio (pic 2). There is no problem with Mozilla on insert image.
Bryan
PS: I can't repeat this behavior here at Moodle.org. Below images were successfully inserted using IE6.