Microsoft Vista VPN Update and Articles

[chicagotech]

Microsoft Vista VPN Update

Please confirm if the server and the client has been upped to date and
installed following updates/hotfixes.

On Client side:
KB930163: In Windows Vista, you cannot access any resources on a remote VPN
server after you switch a network connection from one network adapter to
another network adapter and then dial a VPN connection
http://support.microsoft.com/kb/930163/en-us

On SBS server side:
KB926505: Windows Small Business Server 2003: Windows Vista and Outlook
2007 compatibility update
http://support.microsoft.com/kb/926505/en-us

You may install the updates and recheck the issue.

Microsoft VPN Issues articles

Windows Vista enables the TCP Window Scaling option by default (previous
Windows OS had this option disabled). It's a new feature in Windows Vista.
However some switch or router may drop TCP connections is caused by some
versions of hard firewall not supporting the TCP Window Scaling option. To
avoid this feature effect, please perform the followings steps to disable
it:

1. Click Start , click All Programs, click Accessories, and then click
Command Prompt.
2. At the command prompt, type the following command, and then press ENTER:
netsh interface tcp set global autotuninglevel=disabled
3. Then recheck the issue.

In addition, there are several detailed and useful articles which describes
the similar symptom as yours. And I collected, hope it helps to you:

You receive a "741" or a "742" error message when you try to establish a
VPN connection by using L2TP/IPsec from a Windows client computer to a VPN
server
http://support.microsoft.com/kb/929856

You receive error code 741 when you try to make a PPTP-based VPN connection
on a computer that is running Windows Vista
http://support.microsoft.com/kb/929857

You cannot connect to a Cisco ASA Series VPN server by using an
L2TP/IPsec-based VPN connection in Windows Vista
http://support.microsoft.com/kb/942429

VPN, SecureNat/Nat and Outlook clients not working after installing Windows
Service Pack 2 in SBS 2003 Premium
http://blogs.technet.com/sbs/archive/20 ... and-outloo
k-clients-not-working-after-installing-windows-service-pack-2-in-sbs-2003-pr
emium.aspx