One possible solution I have found is to create a new connection via a .pbk (phonebook) file.
* Create a blank text file on your desktop and then rename it to have a ".pbk" extension
* Open the file (you should see a message saying the phonebook is empty prompting you to add an entry)
* Click Ok
* Select "Workplace network"
* Enter the address to your VPN connection and give it a name and click Next
* Enter your login credentials (optional) and click Create
* With your new connection selected, click Properties
* Verify address on General tab then select the Security tab
* Un-check CHAP options at the bottom and select PAP under "Allow these protocols"
* Select L2TP/IPSec for the type of VPN
* Click the Advanced settings button, select the preshared key option and enter your key then click Ok
* Click Ok to close the Properties
* Click Connect to connect to the new connection
* Enter logon credentials if you did not already do so (optionally select to save credentials) and click Connect
Users who use this type of connection will have to remember to connect via the .pbk file and not via their network connections dialog.
One of the main advantages of this method is the .pbk file can be emailed to your users for easy remote setup - you will still need to verify settings on the security tab and in the test that I did I had to enter the preshared key again after transferring the file to another system.