I’ve just updated JDK on my Mac workstation to the most actual state and tested PD4ML – everything works fine (as before).

Currently Lion comes with no JDK – you need to install it manually. Also Lion does not support 32bit JDK anymore. So I suspect you installed Lion, but JDK remains from your previous installation, which is not compatible with Lion.

The actual JDK can be downloaded from http://connect.apple.com – please give a try.