Ever noticed that sites are way slower in Firefox / Safari / Chrome and so on when you try to debug a website localhost on Vista. Apperently there is some kind of DNS bug caused by IPv6. To fix it in Firefox you can type about:config and look up network.dns.disableIPv6 but this doesn’t fix the issues for other browser.
To fix it system-wide for all browsers edit your hosts file. You find it in %SystemRoot%System32driversetc.
::1 localhost <- Comment this line
Thanks to commenter in this post for this.