Thanks for the reply.  
I have to say that, though I'm unsure of a "how it occurs" I am sure of a "that it occurs" of Original Sin.  If this were not so, the passion and death of Christ would be unnecessary; from what did humanity need redemption if not a common debt?  Baptism would be a silly act since it is given for the remission of sin; we still sin so the only thing that could be remitted is a specific sin, common to all.  
I'm curious, then, if one dispenses with this core element of the faith as commonly understood, both Traditionally and Scripturally, what is the re-imagined "original sin"?  Is Jesus' death and resurrection (provided one still believes this) efficacious or not?