I have just changed webhosts, and am having few probs.

I changed webhosts over 48 hrs ago, yet the dns my end hasnt updated it seems, I keep going to the old cache of the site when everyone is going to the new one that has errors i cant fix because of this. Why is this? I also cant go to certain websites that other people can, for example I havent been able to get to my webhosts site today even tho it works for everyone else, why is this? I have cleared out my cache, history and cookie files.

Thnx