Cannot Access Terminal Server from Home

Windows XP Clients Cannot Connect to a Windows 2000 Terminal Services Server
The information in this article applies to:
Microsoft Windows XP Professional

\Symptoms
When you try to connect from a Windows XP-based client to a Windows 2000-based Terminal Services server, the connection may not succeed and you may receive the following error message:

Because of a security error, the client could not connect to the terminal server. After making sure that you are logged on to the network, try connecting to the server again.
This error message may occur when you try to connect from a Windows XP-based client to some or all of the Windows 2000-based Terminal Services servers in your organization, or the error message may not occur atall.
Cause
This error message is caused by a change in the certificates that are used by the Microsoft Clearinghouse to authorize Terminal Services Licensing servers.
Resolution

To resolve this problem, follow the steps in the following section on the affected Windows 2000-based Terminal Services servers and the Windows XP-based clients.
On the Terminal Services Server
Start Registry Editor (Regedit.exe or Regedt32.exe).
Locate and then click the following key in the registry:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\TermService\Parameters
In this registry key, delete the following values:
Certificate
X 509 Certificate
X 509 Certificate ID
Quit Registry Editor, and then restart the server.
On the Windows XP-Based Client
Start Registry Editor (Regedit.exe).
Locate and then click the following key in the registry:
HKEY_LOCAL_MACHINE\Software\Microsoft\MSLicensing
Delete the whole MSLicensing key from the registry.
Quit Registry Editor.
Connect to the Terminal Services server.

http://support.microsoft.com/default.aspx?scid=kb;en-us;Q323597
Source-

Good Luck My friend

May sound silly. Make sure the client reboots thier computer. If the laptop is put to sleep, it may still contain its IP info from the office.

Also, make sure you are using DHCP in the office, otherwise when he tries to connect to the terminal server he will not use the vpn, he will try to make a direct connection via the network card.

To test, make sure they can ping the Terminal server from thier home over the VPN.

You can do a test from your office, by dialing up.

Well, I don't know what your exact setup is - but this is what I ran across.

I found that machines using the Windows Update (or people actively updating their systems) had installed the latest IE patches. One of them interfers with the TSAC client. There is an update to the TSAC activeX components for the TS server. Once you update the server, the clients are able to connect without issues. I've included the MS link with additional information:

http://support.microsoft.com/default.aspx?scid=KB;EN-US;Q327521&