The problem is that Digg does not accept server-only URLs.
The unit at Digg is stories, not websites.
They have a filter that tries to detect whether an URL is a story or not.
So instead of server.com, I submitted server.com/article.html and it worked:
If you were a user at Digg before they have an archive tool, see more information in the following link
The archive tool is here. I don't know if it's working or not but you can try.
Add index.html1 to the end of your URL and then Digg should accept your submission, it worked for me.
1 or index.htm, or index.asp, or default.htm, or whatever the webserver uses for the default document
Difference is that with Diggs you are publicly upvoting the article or feed item which feeds into what would end up on the main digg.com site based on popularity.
Saves are for your personal stash, and are not used (at least so far) to rank the items that appear on digg.com proper.