I am aware that this is (probably) not an issue related to PW, it's more likely a general issue in TinyMCE (and seems to be well-known among its developers already). I thought I'd mention it anyway:
It is not possible to add images using TinyMCE's "Add image" button at a specific place in an editor's content in IE9. It always gets added at the beginning of the content in the editor, i.e. before the first text paragraph.
I haven't tested it, but it probably doesn't work in IE8, either. Yes, I know there are different approaches of handling inserting images into the content which are preferable.