After three years a new Adler Barbour/Waeco VD-150 Evaporator (West Maring Model #2007292) began leaking a few days ago. The repairman discovered the leak (by filling the fridge box with water instead of removing the evaporator!) to be at the junction of the copper tubing and aluminum tubing near the evaporator. See a picture at http://yachtvalhalla.net/photos/fridgeleak.jpg
Why? Although the basic cause is probably electrolytic corrosion between the disimilar metals, it may well have been exacerbated by the occasional defrosting with salt water in an effort to conserve the limited amount (40 gal) of fresh water we carry aboard.
Waiting for the repairman to seal it with some special 'glue' (which he claims is how the copper and aluminum tubings are joined) we will see what happens.
But we've learned a lesson ... only defrost with air or fresh water!