The Web browser may stop responding when you try to view a Web page that is hosted in IIS 6.0 on a computer that is running an x64-based version of Windows Server 2003

When you try to view a Web page that is hosted in Microsoft Internet Information Services (IIS) 6.0 on a computer that is running an x64-based version of Microsoft Windows Server 2003, the Web browser may stop responding. Additionally, a warning message that resembles the following may be logged in the System event log:

This issue occurs if the following conditions are true:

• IIS 6.0 starts a 32-bit worker process (W3wp.exe).
• The Web site requires Secure Sockets Layer (SSL).
• Client certificate mapping is enabled for the Web site.
• Two or more rules are enabled on the Many-to-1 tab in the Account Mappings dialog box.

To resolve this issue, follow these steps.

Note The following steps remove the certificate matching rules for the Web site.

1. Back up the IIS metabase. To back up the IIS metabase, follow these steps:
   1. Click Start, click Run, type Inetmgr.exe, and then click OK.
   2. Right-click the server that you want to configure, point to All Tasks, and then click Backup/Restore Configuration.
   3. Click Create Backup, type a name for the backup, and then click OK.
      
      Note If you want to encrypt the backup file, click to select the Encrypt backup using password check box, and then type the password that you want two times.
2. Stop the IIS Admin Service service. To do this, follow these steps:
   1. Click Start, click Run, type Services.msc, and then click OK.
   2. Right-click IIS Admin Service, and then click Stop.
3. Open the Metabase.xml file in Notepad.
   
   Note By default, the Metabase.xml file is located in the System32\Inetsrv folder.
4. Locate and then delete each node in the Metabase.xml file in which the Name attribute is UnkknownName_2088. For example, you should delete the following node if it appears in the Metabase.xml file:

   <Custom
   Name="UnknownName_2088"
   ID="2088"
   Value="496344625800000010000000400000009319afe91d1f526d8b613799884407c574c15810b257aff93c6b8c1c8e587247851"
   Type="BINARY"
   UserType="IIS_MD_UT_SERVER"
   Attributes="SECURE"
   />
   

   Note Only delete nodes that have the <Custom> tag and the Name attribute is UnkknownName_2088. Do not delete any other text in the Metabase.xml file.
5. Click File, and then click Save.
6. Exit Notepad.
7. Click Start, click Run, type MMC /32, and then click OK.
8. On the File menu, click Add/Remove Snap-in.
9. Click Add, click Internet Information Services (IIS) Manager, click Add, click Close, and then click OK.
10. Expand Internet Information Services (IIS) Manager, expand the computer that you want to configure, and then expand Web Sites.
11. Right-click the Web site that you want to configure, and then click Properties.
12. On the Directory Security tab, click Edit under Secure communications.
13. Click to select the Enable client certificate mapping check box, and then click Edit.
14. On the Many-to-1 tab, add the certificate mapping rules that you want, and then click OK three times.

After you follow the steps that are listed in the "Resolution" section, you must use the 32-bit Microsoft Management Console (MMC) to view the certificate mapping rules. If you configure IIS 6.0 to start a 64-bit worker process, you must repeat steps 1-6 in the "Resolution" section. Then, re-create the certificate mapping rules in the 64-bit version of IIS Manager.