This sure sounds like the rear differetial on the tranny is shot. You drive 10 miles and the clutch pack heat up and then won't release going around a turn. Wheel bearings won't clunk they hum (as posted earlier) when they get load goiung around a bend at speed. A bad CV joint won't take ten miles to "thunk"
Try removing the rear drive shaft. Not sure how the forester is set up but if it is like the Outback then just remove the rear half of the shaft. The front half will hang from the carrier bearing and stay out of the way.
Once the front and rear wheels are seperated you should notice the binding going around bends. If this isn't the problem then you can reinstall the drive shaft and keep looking.
Hope this helps,
Peter