Try pulling the e-brake up like you would to park the car on a hill. There are two cables going back from the bracket with the adjuster bolt, push each one sideways. If there's slack in one of the cables then the problem is almost definitely the cable that's slack.
If they're both the same tension then either there's something wrong with your rear brake (the one that doesn't get stopped by the e-brake) or your cable housing is rusted up (internally). Check the rear brakes to see if the cable is connected on the side that won't stop, if it's not but the cable is still tight then the cable is your problem, if it is then the problem is most likely in your rear brake.
Hope this helps, it's way too in depth, but TMI is generally more useful than too little.
Sometimes the cables get stretched too. If that's the case, you may not be able to adjust it properly until you replace the cable on that side. Try adjusting it first. There's a an article about how to do this in the HOW TO section.