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Procedure:
1) Download the current Vodafone Web Session scripts and unzip the ZIP file. This contains three script files.
vodafonewebsession_scripts.zip
2) Open the Windows Explorer and go to the script directory of Advanced VPN Client (default: C:\Program Files\LANCOM\Advanced VPN Client\Scripts).
3) Delete all of the existing Vodafone Web Session scripts in this folder (usually 4 files) and then copy the three previously unzipped Vodafone Web Session scripts into this folder.
4) Open the LANCOM Advanced VPN Client and edit your VPN-UMTS profile in the dialog Configuration -> Profiles.
5) In the profile, select the menu item Line management from the menu tree and enable the option HTTP authentication. A new item appears in the directory tree, HTTP logon. 
6) In the HTTP logon fields you can now enter your access credentials and select the appropriate script file. 