I have found several small fixes that on different PC's work. There is ONLY one fix that solves the problem fully but involes more time and effort.
Simple fix One
Check the version of JAVA currently installed. If version 6 then try this. Open internet explorer 9> TOOLS then INTERNET OPTIONS, select the ADVANCED tab and scroll down to Security section and tick "Allow software to run or install even if the signature is invalid" Click OK and restart IE and try VPN.
Simple fix Two
If above fails to solve the problem, try this. Logon to the PC as local administrator, connect to the internet and download and install the lastest version of JAVA 7.51 restart the PC open control panel and open JAVA check it's 7.51. then click on the security tab. Click the "Edit Site List" and add in your VPN url eg https://mysiteurl.com then move the security level slide to medium and click OK, restart the PC and test VPN.
Big Stick Fix
If all else fails, try this. Logon to the PC as local administrator. Locate the users profile that is having the problem and copy it some where safe C:\Support as an example. Once you have a safe copy of the users Profile, Click the Computer icon, right click and select properties, then Advanced system settings. Under the User Profiles click the settings button, locate the user, highlight and delete profile. Reboot the PC, log back on as the user this will recreate the profile. The VPN should now work correctly. You can copy back Favourites, documents, picture etc, etc from the saved profile in this case from the C:\Support folder.
I hope this helps...
