Physics Volumes no longer work correctly with Deathball1.7. DavidM so far has blamed it on may errors but, it is a 1.7 bug. If your maps contain physics volumes with paincausing including water, slime, and lava volumes, they most likely won't work correctly with 1.7 installed.
I find that this works, but not correctly in 1.8. It takes longer to die than it should. A physic volume set at 100/sec should be an instant kill, however a player can get well inside the volume. Anyone else notice this.