I can access my local dev site on my local pc, eg:

http://mysite

But I cannot access the live site, even though it works fine on other pc's:

http://www.mysite.com

The live site gives the error in Firefox: Server Not Found. Pinging www.mysite.com gives the error:"Ping request could not find host www.mysite.com"

hosts file:

127.0.0.1   mysite

I changed the hosts file to the following and rebooted:

127.0.0.1   mysitedev

I'm running on XP, and have cleared the DNS cache using:

ipconfig /flushdns

I have verified the live site is up using:

http://www.isup.me/

and the site loads fine using my phone.

What could be preventing my local pc from accessing the live site?