Greetings!

At a guess, it sounds like there might be something sick in the database or you need to fsck your drives. Possibly both. I would recommend that you follow this to make certain your filesystems are in good shape. I know you have already drived to delete and rebuild the database like this.

Do you see any error messages on an open console window when you try these syncs? I am wondering if you are getting any filesystem or disk errors being printed. It might be the sign of something else wrong.