Vista VPN Issue

Please could some one help!

I have been using Windows Vista Ultimate for about 2 months now. I been
accessing 3 VPN's off this machine however since last week I have been
unable to connect to the VPN's

Nothing has changed regarding my computer configuration.

When I try and access a VPN it is freezing at the "verifying username and
password" screen and then I get an error 734.

I have read up on some forums and have seen other people with this issue
however I have not been able to find any solution for this.

Would be most grateful is some one could shed some light on this.

Things I have Tried:

*Deleted current vpn setup and re added it.
*Unchecked IP V6 on vpn and Ip config.

*I HAVE TESTED THESE VPNS WITH XP CLIENT AND IT WORKS FINE*

Many Thanks