RWC -sevens

What is it about RWC that so often makes NZ rugby falters? even their sevens team falter at the quarter final stages? I was planning to watch the RWC sevens in TV.. but when i heard that NZ lost to Wales... I wanted to puke... not again.... the must have some voodo with RWC wether its 7s or 15s.... ah well at least I watching house tonite