Please read this article before proceeding.

To disable IPv6 for Mac OS X:

1. Click on the Apple Menu and scroll to System Preferences.
2. Select the Network preference pane.
3. Highlight your active interface (such as Ethernet or Airport).
4. Click Advanced.
5. Set Configure to IPv6 to Off.
6. Click OK.
7. Click Apply.

Please note: If you have multiple network interfaces, you will need to repeat this procedure for each interface.