[rpspringuel]

You have a permission error witht he file metadata.calibre that's on your Kindle. Try deleting that file and see if it works. Also with the Kindle plugged into the USB port, (without Calibre running), check the Kindle filesystem for errors.

I tried all of that before posting. Couldn't find any problems, but still was getting the errors.

Also check the permission for /Volumes/Kindle 3/ and see what's going on.

Permissions indicate that rwx for user and r-x for everyone else, the same as all other external drives connected to the system.

This is not a Calibre problem. It's something either on your computer or the Kindle.

If it's not a Calibre problem, then why does the problem only occur when Calibre is running? The Kindle connects to the computer just fine when calibre isn't open.

Another thing to try is to give a factory format to the Kindle and then see if it works from there.

Tried this. Still seeing the same error, but it isn't all the time now.

I've got it working at the moment, and checking the permissions I see that the current mount point has rwx access for all users (not just current) but the group is just me (not admin). So I guess this is a permissions issue, and calibre, for whatever reason, isn't considered a current user operation when it tries to write (raising the permissions error). Whereas anything I do through Finder is (and thus works). Why that would cause a force removal of the Kindle, I don't know, but it's what appears to be happening.

So, maybe not a calibre problem, but still one that's only showing up in conjunction with calibre and has me stumped.