hmmm, when you say it spits them all into the shooter lane at once, do you mean it launches each one individually before the game starts, and never stops loading and launching? because that usually means a diverter in the subway isn't working.

Take all the balls out and enter switch edge test. Drop the balls in one by one and watch the display. All switches should transition as the ball rolls by. Verify they all toggle and then remain open.

Then take a piece of paper or something and trip the Trough Jam opto that's in the chute leading from trough to shooter lane. When the Jam opto flakes out it makes the game shoot perpetual balls onto the field.

Just had this same problem on a friends sttng this weekend. He had new trough opto boards and we found a wire had come out of the receiver board plug. New board had led for each ball, that would go out when balls where installed and nothing was lit up so it was easy to see no power to board.

Time to change your Pinside avatar to Tales From The Crypt John.
This is Bill, Jeff's buddy you met yesterday. We'll try these fixes.
Thanks for the post!

In addition to opto issues, Do you have right number of balls in the game? Go into switch edges and see what's active.