Plugin Version: 4.3.0
WordPress Version: 3.4
It looks like Socialable is using Google functionality that is no longer supported on Google Reader and it produces a 404 on every post that has the plugin enabled on it.
The link to Google Reader (icon) is what produces the 404 as follows and Google reports the following:
We're sorry - Google Reader no longer supports the "Note in Reader" bookmarklet.
I thought disabling the Google Reader Icon would stop it but it doesn't. Why? Because it puts the Google Reader icon in the "+MORE button and the link is still there.
You can see the response from Google by looking at this page