This one posted on here http://blogs.technet.com/b/isablog/archive/2010/05/31/authentication-delay-for-sites-published-through-isa-server-2006-using-forms-based-authentication.aspx i.e. our product team blog site.

Issue: At the end of installation of TMG 2010 getting error “The Microsoft Forefront TMG services cannot be started. Please try restarting the computer.”

Troubleshooting:

In the event logs if we find following event

Log Name: Application

Source: Microsoft Forefront TMG Control

Date: 12/01/2010 02:05:09 p.m.

Event ID: 14192

Task Category: None

Level: Error

Keywords: Classic User: N/A Computer: TMG1.contoso.com.

Description: The Microsoft Forefront TMG Control service failed to start because the operating system service Internet Connection Sharing (ICS) is already running. To fix this problem, stop the Internet Connection Sharing (ICS) service, start the Microsoft Forefront TMG Control service, and then restart the Internet Connection Sharing (ICS) service. Event Xml: <Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event"> <System> <Provider Name="Microsoft Forefront TMG Control" /> <EventID Qualifiers="49152">14192</EventID> <Level>2</Level> <Task>0</Task> <Keywords>0x80000000000000</Keywords> <TimeCreated SystemTime="2010-05-12T19:46:09.000Z" /> <EventRecordID>7516</EventRecordID> <Channel>Application</Channel> <Computer>TMG1.contoso.com</Computer> <Security /> </System> <EventData> <Data>Internet Connection Sharing (ICS)</Data> </EventData> </Event>

Resolution: Disable and stop the Internet Connection Sharing (ICS) service and then start the TMG services and the services would start fine.

Another quick bit about what is supported with a single NIC ISA server in terms of VPN

as per unsupported article http://technet.microsoft.com/en-us/library/cc302678.aspx

"Site-to-site virtual private networks (VPNs) are not supported in a single network adapter scenario. Remote client VPN access is supported in a single network adapter scenario"

i.e. Remote client VPN would still work with it.