Can you export a short section of your timeline successfully? If so, then the simplest next step is to clean the Media Cache database. Close and save your current project. Create a new dummy project and go to Edit>Preferences>Media and press the Clean button. See if you can export the full timeline. If you can't export even a short section, then it's time for more fundamental cleanup and troubleshooting steps. Read this document:
"Error compiling movie" when rendering or exporting with Premiere Pro CS3, CS4, CS5, CS5.5, CS6
Follow it and its associated documents all the way to conclusion. Warning: it's not pretty.
Jeff