Please refer to the Apple website http://www.apple.com/au/support/iphone/ for any additional troubleshooting support.
Please note: Apple has an exchange program involving the Apple Ultracompact USB Power Adapter sold with the Apple® iPhone™ 3G S and 3G in certain countries. Adapters sold with the Apple® iPhone™ 3G S and 3G through Vodafone Australia are NOT affected by this initiative.
If you have purchased one of the adaptors outside Australia, or if you would like to know more, you can find information about the Apple Ultracompact USB Power Adapter Exchange online at:
http://www.apple.com/support/usbadapter/exchangeprogram/