Sorry you can't fix it. Most games are Region specific meaning that they are playable only on Xbox 360 systems from the specific region that you have. If you bought your Xbox 360 in Australia then it is likely PAL system and can only play Pal games.
"Determine whether the game disc is from the same region as the region where you purchased the Xbox console. To determine the region, view the back of the game package. Look for one of the following codes:
* NTSC: North America and South America (United States, Canada, Mexico, Chile, and Brazil)
* NTSC-J: Asia (Hong Kong, Japan, Korea, Singapore, and Taiwan)
* PAL: Europe, South Africa, India, Australia, and New Zealand"
If the game you have doesn't match with your Xbox 360 Region then you won't be able to play it. (but a few games are playable on multiple regions, check list below)
Check out this site prior to buying games to help identify which games that aren't PAL might be still playable on your system.: http://www.play-asia.com/paOS-00-3-xbox360_compatibility_guide-49-en-84-t.html
Notice that NBA 2K8 US version is not compatible with PAL system. If you had bought the US version of NBA 2K9 then it would have worked.