I am still stuck here. Can you check the secure section of this reply, if you have a moment?
EDIT: SOLVED!! finally.
This was related to the geshi plugin. As soon as I removed this plugin, created a new backup, restored to a new subdomain...database restoration worked without throwing the error.
So it's related to Joomla, not RocketTheme. Since Joomla 3.2+ uses CodeMirror, it causes no problem to remove it (I think it's only there for legacy purposes). But because it is outdated, it is referring to directories that are no longer on the server, and causing the error.
This is the thread that helped me solve it, just in case someone else runs across the same issue (however, if you are prudent about updating things, you probably would never have the problem in the first place):
http://forum.joomla.org/viewtopic.php?f=431&t=288136&start=90
Particularly this:
Step 1. Identify which plugin is having problem:
You can either disable those plugin one by one in Administration control panel under Extensions -> Plugin Manager. When you disable one plugin and the error doesn't show again when editing post, then this is the plugin in problem.
You can also go to Extensions -> Install/Uninstall -> Plugins
Look for those plugins which its "version", "date" and "author" column is empty. These are the plugins in problem.
Step 2. Remove the plugin which is having problem:
You can try to uninstall the plugins under "Extensions -> Install/Uninstall -> Plugins", although you will see error uninstalling, you may try if you can edit post now to see if the Fatal error persists. (this works for some people, but for my case, the error persists)
If the error persists, you need to delete the plugins from your MySQL database table directly.
Go to your MySql database and open the "jos_plugins" table, delete those lines which the plugins are having problem (those you identified in Step1).
Step 3. You can now re-install the plugins:
At Adminstrator page then select "Extensions -> Install/Uninstall".
From here you can re-install the plugin and it will be working properly.