SBS 2003 no network access after restart

The problem is that DNS is grabbing all the available TCP ports following a Windows Update

If IPSEC is affected it goes into Block mode which prevents any unsecured network traffic to\from the server.

The solution is to add ports to the ReservedPorts list in the registry.

Source URL:
http://support.microsoft.com/kb/956189

To resolve this problem, add the port that is needed by the service to the ReservedPorts registry value. This prevents the DNS Server service from listening on that port. The following ports are known to cause conflicts:
Collapse this tableExpand this table
Ports Program that uses the ports
1645-1646 IAS
1701-1701 L2TP
1718-1719 H.323 Gatekeeper (ISA 2000 only)
1745-1745 ISA Server 2000 or ISA Server 2004
1812-1813 IAS
2883-2883 AUTD
3500-3619 ISA Server 2000 only
4500-4500 IPSEC
To configure the ReservedPorts registry value, follow these steps:

1. Click Start, click Run, type regedit, and then click OK.
2. Locate and then click the following subkey:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters
3. Right-click ReservedPorts, and then click Modify.
4. Type the range of ports that you want to reserve.

Notes
* You must type the range of ports in the following format: xxxx-yyyy
* Do not replace the existing values. Instead, add the additional values.
* To specify a single port, use the same value for x and for y. For example, to specify port 4000, type 4000-4000.
* If you specify the continuous ports separately and if one port is reserved and is not used, the next port is not reserved correctly, and the port is used.
* ISA Server settings only apply to Small Business Server 2000 or to Windows Small Business Server 2003 Premium Edition.
5. Click OK.

Restart the server and things should be sorted.