Virtually all my posts go via Postie (1.5.3). Generally works great, but recently an odd problem has arisen where attached image files (usually JPGs) do not display in the post - instead a placeholder appears with text inside which is the attachment filename (minus ext.).
This does not happen with all posts, and I cannot see any reason (e.g. file size) why some work fine and some do not.
The attachments affected in this way also present oddly in the media library - they appear as grey block thumbnails, but when selected for edit, appear normally.