I registered because I had the same problem, but have since found a solution, to my problem at least.
With the latest upgrade (4.5.1), I lost my Digg Digg as well.
When I clicked to set up normal display, I saw this:
Fatal error: dd_page_for_normal_display() [function.dd-page-for-normal-display]: The script tried to execute a method or access a property of an incomplete object. Please ensure that the class definition "DD_Sphinn" of the object you are trying to operate on was loaded _before_ unserialize() gets called or provide a __autoload() function to load the class definition in /home/sdname/public_html/wp-content/plugins/digg-digg/include/template/dd-template-normal-display.php on line 63
Same happened for floating.
What I did to fix it was delete the "sorting" foreach loop in the code which made it so that none of the options showed up BUT the page did display. With the page loaded, I could "enabled" it. I put the code back, reloaded it and it worked fine.
So it seems that if it's never been enabled or there are no options are you try to access the page, it breaks. Hacking and then enabling it fixes it.
Now I have the options page and the floating links appearing normally.