The solution to this problem can be found here:

http://www.velocityreviews.com/forums/t29443-cannot-access-internet-while-connected-thru-vpn.html

1. Bring up the properties of your VPN connection and select the [Networking] tab.
2. Select the Internet Protocol Version 4 or 6 Properties and click the [Advanced] button.
3. Make sure that [Use default gateway on remote network] is not checked.
4. Click the [OK] button to save your settings.