The question of whether or not photons have mass is not really that important to this discussion is it? The question was whether souls have mass, and more generally whether anything can exist that does not have either mass or energy. If photons do not meet the qualification of something that has no mass that doesn't mean souls have mass, unless we are sure souls are made out of photons.
If a soul is just information though it can exsist without mass or energy. It might take some energy to transfer it from one form of storage to another, and it's presence might cause the mass of the storage or transmission medium to alter position. But that doesn't mean the information itself has mass or energy. And it wouldn't require any fancy transdimensional particle waves or anything.
[ August 18, 2003, 17:10: Message edited by: geoschmo ]