ISA 2006 clients are repeatedly prompted for credentials when they try to access Outlook Web Access

Microsoft Internet Security and Acceleration Server 2006 clients are repeatedly prompted for credentials when they try to access Microsoft Office Outlook Web Access (OWA).

Additionally, if you try to run the Netdom.exe query fsmo command or if you try to run any remote procedure call (RPC)-based tool on the ISA server, you may receive the following error message:

This problem occurs when the following conditions are both true:

• Windows Server 2003 Service Pack 2 is installed on the ISA server.
• You configure a publishing rule to redirect traffic to the Exchange front end in the internal network for authenticated users.

Warning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall the operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.

To resolve this issue, use Method 1. If Method 1 does not resolve the problem, also use Method 2.

Method 1: Configure the EnableRSS registry value and the EnableTCPA registry value

1. Click Start, click Run, type regedit, and then click OK.
2. Locate and then click the following registry subkey: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters
3. On the Edit menu, point to New, click DWORD Value, and then type EnableRSS.
4. Double-click EnableRSS, type 0, and then click OK.
5. On the Edit menu, point to New, click DWORD Value, and then type EnableTCPA.
6. Double-click EnableTCPA, type 0, and then click OK.
7. Exit Registry Editor, and then restart the server.

Method 2: Configure the DisableTaskOffload registry entry

If you continue to receive RPC errors, follow these steps:

1. Click Start, click Run, type regedit, and then click OK.
2. Locate and then click the following registry subkey: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters
3. In the details pane, make sure that the DisableTaskOffload registry entry exists. If this entry does not exist, add the entry. To do this, follow these steps:
   1. On the Edit menu, point to New, and then click DWORD Value
   2. Type DisableTaskOffload.
4. Double-Click DisableTaskOffload, type 1, and then click OK.
5. Exit Registry Editor, and then restart the server.