Reproduced in FF3, IE7, and Safari 3 for windows. Reproduced using this example: http://developer.yahoo.com/yui/examples/editor/flickr_editor.html:

1) Click on the insert image button. Insert an image into the document (inthis example I use ).
2) Close the insert image window. Resize the image
3) Reopen the insert image window and click on the window pane (anywhere that's not the insert image url text field). The image size text fields reset to the original size.

It is undesirable behavior for the image size to change if you click the window. Moreover, the actual image size does not change unless you invoke blur the height and width text fields, which is
inconsistent.

I believe this is being caused by the insert image url text field being set to focus when the window opens, and a bug in the insert image url text field's onblur() event which updates the image size
even if the image url has not changed.

The expected behavior is that the image height and width text fields do not change if the image url has not changed.