I renamed both the media.xml on the internal device and the cache.xml on the memory card. Then rebuilt. But I still get the message on connection.
ERROR: Device database corrupted:
<p>The database of books on the reader is corrupted. Try the following:
<ol>
<li>Unplug the reader. Wait for it to finish regenerating the database (i.e. wait till it is ready to be used). Plug it back in. Now it should work with calibre. If not try the next step.</li>
<li>Quit calibre. Find the file media.xml in the reader's main memory. Delete it. Unplug the reader. Wait for it to regenerate the file. Re-connect it and start calibre.</li>
</ol>
how do I check the internal memory for File system errors?, via explorer?