Hi Tim,
I tried again - but with a similar error code this time.
1. Added a Book to Calibre from Digital Editions
2. Sent it to the device
3. Removed the Koko Reader
4. Inserted the Kobo Reader
5. Tried a delete
6. Got this slightly different error message
7. Still can't copy the error to the clipboard....
Hope this helps....
Cheers
John