I have a bunch of questions. Maybe your answers will help me or someone else figure out what's going on:
1) What did the old fluid look like? Was it dark-colored? Did it smell burnt? Did the fluid look like water was mixed with it?
2) When you took the pan off did you find any large chunks in the bottom? In some pans there's a small donut-shaped magnet in the bottom of the pan. Were there any large particles of metal stuck to the magnet? Some small particles in the bottom of the pan or on the filter are to be expected and are not necessarily a sign of impending transmission failure.
3) When you were under the car did you see if the throttle linkage was hooked to the lever on the transmission?