Apparently there is an error in the WP v 3.6 when you try to edit/update your old blog post.
The error message you get is:
“Connection lost. Saving has been disabled until you’re reconnected”
The answer to this problem lies in your wordpress plugin(s).
Delete all unnecessary plugins. Yes, we all have them. These are plugins that just lie there doing nothing. Just trash them.
Note: DO NOT delete the plugins you are already using (the ones that are activated).
Now try and update your post and you will see that you can easily update your posts and pages now.
If that did not help then update all the other plugins (the active ones).
Still no solution?