Was there a little bit of tape you had to pull out from the battery compartment when you first used it? I'm clutching at straws, as I can't remember it on mine, but as Sam said, it could well have been some sort of contamination of the battery terminals, which you have now cleaned.
Obviously, it's up to you whether you return it, but personally, I would probably give it some more use, and see if it happens again, rather than having the hassle of an exchange, unless, of course, you bought it locally, and can just take it back to the shop. Remember, you have a year's warranty, so my suggestion would be to give it a month or so, with good usage, and if it happens again, it would definitely seem that a fault is present.