The status is a standard routine with items being shipped out of (and into) New Zealand. Customs in either NZ or the country of destination are holding onto the item on a short term basis (usually 1 -3 days) to ensure all of the requirements have been met before allowing the package to pass on. Reasons why customs holds on to things include making certain tariffs and taxes are paid, the package does not include underiable elements (ex - narcotics, hazardous materials, flora/fauna which may pose problems crossing borders, etc), and other typical governmental red tape.
I lived in NZ for most of 2007 and this is really quite normal. Once everything clears, the package will find its way to you in no time. Unfortunately, the Kiwi post office can't do much to speed things up for you, but their website should still contain information about why packages get delayed.