I installed SR4.1 tonight and loaded some new lights and primitives and the Depth Map Shadows have returned. Opened one of my old shadow test files (where the depth map shaodws first disappeared) and rendered it, and the Depth Map Shadows worked! Turns out, when I was doing my update I noticed that I had SR4 already, so this problem WAS the DM shadow issue people were having trouble with. SR4.1 with shadows... opens faster... renders faster... live is good again!