Non-functional Jetstar Online system

In attempting to book a flight via the web with Jetstar, it appears there is no way for me to actually register in their system. As an existing Qantas frequent flyer customer, I am asked to enter my Qantas user id and password. For Qantas my user id is my frequent flyer number. But Jetstar's system then rejects that user id as it is not a valid email address. I attempted to contact Jetstar about this, but they do not appear to have any way to do so in writing, apart from sending them a paper letter through the mail. Jetstar do not appear to accept email or messages viw their web site. Perhaps it would be simpler to travel VirginBlue.