Error message: "Destination directory is not writable"

I'm attempting to add items to the site and the above message pops up and will not allow the file or any information I place in Dublin Core to save.

That sounds like the files directory (and its subdirectories) is not writable by the server. I'd check the permissions on those directories. In rarer cases, the directory in question is the /tmp directory, which would need a server admin to look at.