Okay, now I have never used the CPanel for this before, using phpmyadmin you backup everything in one file. I don't want to make you confused but if you backup everything and then re-install your IPB, you simply import the old database, and then you have all of your users/posts etc. The thing is, I believe have to install the exact same forum software.
Again, I'm really sorry if I'm confusing you, but what I am getting at is I recommend using phpmyadmin, doing a full reinstall of your forum software (Because I do not know what exactly you or the software did to make things go wrong) and then reupload the database.
If you would like, I could add you on my skype, and we can instant chat about this. If not, thats cool too
Tyler's post in IP.Board 3.4.2 Language, and Re-installation Support was marked as the answer