@(you need an account to see links)
Generally automatic re-directs are a symptom of a virus, but if it's gone away that is really odd. It could be you picked up something and whatever security system you have just took awhile to clean it up. Hard to say really. If it was just neopets.com that caused the re-directs and no other website, then it's likely that someone was playing around with the site, and has nothing to do with your computer. Hard to tell.