Unfortunately we have had no end of problems with Trade Me sellers, and we have only been here 3 months
Our problems have mainly been over items misdescribed, and not being in as good a condition as the ad states. A pair of skis arrived with a major repair and lots of scratches which was not mentioned on the listing (infact described as in excellent condition), two pairs of ski boots arrived (from different sellers), both different from the sizes advertised, and a tablet PC which was described as only having been used twice, had clearly been dropped and had far more use than the seller stated.
Most of the sellers refunded our monies no problem and paid for return postage, or we didn't go ahead with the transaction if we saw the item in person. The 2 sellers that decided to ignore us got negative feedback after a week stating the problems and their lack of response, I also emailed Trade Me to report them.
After a week or so, and if they are still ignoring you, you can take the seller to a disputes tribunal (about $30). Fortunately as soon as we have threatened sellers with a disputes tribunal they usually spring to life and get the matter sorted out - although begrudgingly.
Hopefully this is a one off for you and you won't have any other problems, as I think we have just been unlucky!
My real bug bear with Trade Me though is the lack of a cheap and secure payment method such as paypal to help safeguard transactions.... as kiwis tend to just transfer monies straight into the sellers bank account!
Good luck getting things sorted.