On Mac:
Make sure you are logged in as administrator
Open Finder
Hold down COMMAND + SHIFT keys and press G
Enter /private/etc/ in the field and press Go
Find hosts file in the directory
Drag the file to your desktop
Open it in text editor
Remove the line that has gs.apple.com entirely or put a # at the beginning of it to comment it out
Save the file
Drag it back to the /private/etc/ folder
Enter your username and password to authenticate
On Windows:
Locate the hosts file in one of the following directories:
Windows 95/98/Me c:\windows\hosts
Windows NT/2000/XP Pro c:\winnt\system32\drivers\etc\hosts
Windows XP, Vista, 7 c:\windows\system32\drivers\etc\hosts
Right click on it and choose Open With
then click on Notepad
Remove the line that has gs.apple.com completely and save the file