If you dig down into the HTML, you’ll see that the buttons are there but the background images that make the buttons are not. That’s because they’re looking for their background sprite image in the following location:
/dev/wp-content/plugins/sociable/images/sprites/option1_16.png
I’m assuming, therefore, that you either just moved the site from a /dev/ folder or are storing WordPress in a /dev/ folder and redirecting the root URL.
If the former is the case, I’d recommend uninstalling and reinstalling the plugin to see if it had saved a setting in some weird way and that fixes it.
If it’s the latter, make sure you’ve completely followed the instructions for Giving WordPress Its Own Directory. It’s easy to skip a step and problems like this are usually what arise from that.
It’s also possible that the issue is a bug with the Sociable plugin affecting sites installed in a subdirectory or that there’s some setting in Sociable causing the issue (for some reason they’re not appearing in the plugin repository right now so it’s hard to figure out what settings they provide).