Parsing Different Domains

Hi everyone, I have a puzzling problem that I can't seem to find a reason or solution. I have a simple (identical) PHP page placed in two different directories of two different domains (on the same RaQ3 machine - different IP's). One of them works as it should, the other says that "The page cannot be displayed". The problem site will show non-PHP pages without any difficulty. I can't see why any of the directives would effect this? Any suggestions as to where to start looking? Bryan