As Rock said, to quote the RuleBook:
14.3.5 A Classic Flight Reward Itinerary must contain no more than one departure from the city or country of first departure on that Itinerary.
If you want to break up the itinerary, a useful strategy is to start in SE Asia (say a LCC to KUL), then onward to Europe, return to Oz, then over to US, then return to KUL. The itinerary stops there, and you LCC back to Oz.
You will need to keep an eye on the mileage though...
For a summary of the various rules, take a look at the wiki at the top of the page.
Thanks for that. I guess I was hoping the definition of "departure" was different from "transit".