I searched for import invalid, but only got one result which is different from what is happening for me.
I was a couple of versions behind on the theme and just updated to 3.6.7. (Already had WP 3.2.1) Prior to doing this I exported the settings file. On clicking Import/Export after updating the theme I found that the file now needs to be pasted in. When I pasted in the code I was told that it seems to be an invalid file. How do I get my settings back?
My header graphic was gone too, but I got it back.