Tipically when this happens the PC generates a core dump after it has restored itself, you would need the windows debugging tools to decode that dump and find out the specific component that crashes with your vpn client. If you manage to get that core dump, I would look at the file it makes reference and google it, or open a tac case, it will also help to have details of your PC such as brand, OS type, OS version and platform, firewalls, antiviurus and stuff.
