The forums can be a bit finicky. The first thing to make sure is that when you search, click on the magnifying glass icon. Hitting enter doesn't always submit the search properly.
Alternatively, the forum entries are indexed so you can search google by typing: "site:www.clearcanvas.ca mpr".
If you're looking for an overview of the mpr feature, we do have a video: http://www.youtube.com/watch?v=GSJHohSjXd0
Hope that helps.