Solved my problem, <?php wp_head();?> was missing from my header file!
I’m having the same issue as well. Prior to the problem I was trying to swap out jQuery for the latest version. I should have restored my code to its previous state now, but now the Sociable and I Like This plugins don’t seem to be picking up the CSS. I tried pasting the CSS into my main stylesheet, and that works! But I would also prefer that the plugin CSS be kept separate.
