After the upgrade to 3.5, scheduled posts that contain an apostrophe or quote marks are published with a slash prior to them: such as you/'re. This does not happen on immediately published posts, only scheduled posts.
I deactivated all plug-ins and tested the scenario with each plug-in: it only happens when Tweet Embed is activated.
This happens whether or not the post contains an embedded tweet.
Let me know if you need more information.