Just used this guide to repairing the regulator. My issue was that the window wouldn't quite drop enough to clear the trim when opening and closing the door. I don't think it's a stretched cable, more like a piece of plastic in the regulator fails leaving slack in the cable. Fixed with a brake cable adjuster from a bike. Works well. Link to guide below.
http://986forum.com/forums/boxster-...-regulator-permanent-fix-stretched-cable.html
http://986forum.com/forums/boxster-...-regulator-permanent-fix-stretched-cable.html