I noticed with 2.3 today that if you use IE7 to wrap text around an image/thumbnail, it deletes the image from being visible in the Rich Text Editor.
I tried it on two different PCs running IE7.
Here's the Jing screencapture of it happening.
http://screencast.com/t/eaosJpSse
I asked a colleague about it and what he suspects
is some sort of javascript quirk where empty dimensions mean “null,” it won’t allow “null,” so it fills in “1”—thus making the image 1×1.
To my knowledge, it hasn't been happening with previous versions of WP.
It doesn't happen with FFox.