Martin,
No, I'm not sure what caused the failure. My guess would be heat/lubrication, as the ends of 3 of the little gears are sheared/welded into the side plates, but it had plenty of lube when I drained it. I wonder if my 2 day, cross country trip hastened its demise, but hard to tell.
To avoid the cost of replacing it, I attempted to venture down the path of having a new 2 piece driveshaft made, but it's almost 1/3 the cost of a new reverse box. I also considered just welding the internals of the box together and using it as a large carrier bearing to reuse my existing driveshafts, but I didn't have confidence that the welds wouldn't break, so I investigated having a new 1 piece splined shaft made to go through the reverse box, but that too was about 1/3 the cost of a new reverse box. After talking it over a bit with a friend, he pointed out that it'd be hard/possibly unsafe to get the car in/out of the garage w/ my sloped driveway without reverse, so I'm going to hold off and probably end up buying another Quaife. My existing one is an early unit, I've heard that they have made some improvements so hopefully I wouldn't grenade a 2nd one.
As to the pictures, I tried posting links to my Photobucket account, but I still got a message saying I couldn't post that many links, my guess is it's an anti-spam measure. I've moved them all into their own album, the link is below.
http://s728.photobucket.com/albums/ww290/crturboguy/Locost/ReverseBox/
--JOsh