I have located the problem. It depends on Internet Explorer. If I use Firefox, I do not have this problem.

To clarify.
I have in my application the ability to enter into a box the image width and height, before you uploaded a picture. Internet Explorer remembers (caches) and apparently the Insert Image dialogue shows the first value of the image I uploaded. I change the width of the image and upload the same image again appears in the fields width and height of the first value (whether I close the browser).
The value at "Max image dimension is 640 ... .." is correct and the image may be the value on the server.
I try to insert the image in the editor using the Insert Image shown is still the first value, which is incorrect.

To localize the problem, try uploading the same image (overwrite) and change a couple of times:
Editor1.Setting ( "security: MaxImageWidth") = "300"
Editor1.Setting ( "security: MaxImageHeight") = "200" using Internet Explorer and see if you get the same values in the Insert Image dialogue text boxes width / height that you specify in MaxImageWidth ... ...