If you paste image map code into the HTML editor, and then switch to the Visual editor, it messes up the image map code by wrapping each <area> tag with duplicate <map> tags.
This also happens on WP 3.2 but didn't happen on WP 3.1.
Note the image map code IS being pasted into the HTML editor but if you switch to the Visual Editor for any reason to make other changes, it alters the image map code. Even if you don't make changes - paste image map code into HTML editor, switch to Visual, then switch back - the image code is altered.
The setting for "WordPress should correct invalidly nested XHTML automatically" is also OFF.