I had the same problem with sociable and several other plugins not working properly,
I used the Clean Options Plugin to find all the unused options left over by plugin uninstalls. There was an orphaned option that had no name to it, and I think this might have been the problem. I had to remove that one from the database by hand using phpMyAdmin. It took a little work, but as soon as I cleaned the options table I reinstalled sociable and it started working. Hope that might help.
