Hi Tango,
I'm probably being really dense, but I can't seem to duplicate either of the issue's you're experiencing. Here's what I've tried:
Edit page with Windows Live Writer and add an image.
Edit the same page with the Telerik editor online and add an image.
View the page in a browser to see if the image expander still works (it does).
Open the page again in Windows Live Writer to see if I have any problems editing the content.
Also, when I edit pages that use the de-DE locale, I'm taken to the de-DE edition of the page after editing.
What version of metaPost and Magic Content are you using? I'm using the latest version of metaPost (1.2) along with the 4.0.0.1 version of Magic Content.
Thanks and sorry I'm not able to duplicate this right away!
Don