We couldn’t sign you in
Select the account you want to use.


You have a server that is running Windows Server 2008 R2 Service Pack 1 (SP1), and you have an application that depends on the Microsoft Lightweight Directory Access Protocol (LDAP) client to obtain information from a directory service. One example for such an application is Microsoft Exchange Server.

The symptom for Exchange Server is as follows:

When CPU usage for the Microsoft Exchange RPC Client Access service spikes to 100 percent, all connected Microsoft Outlook clients are disconnected. Additionally, new Outlook client connection attempts are unsuccessful.

Additionally, the w3wp.exe and store.exe processes may freeze.

When these issues occur, event 2070 is logged together with error 0x55 on the Exchange server:
Note This frequently occurs if the event is logged for other reasons and does not indicate this problem type behavior. You also do not have this issue if there is a different error code (such as 0x51 or 0x34).

You are likely to encounter the problem that is discussed in this article when you see multiples of these events logged in a short time for all the domain controllers that the Exchange server has access to. Also, the services of Exchange eventually stop making progress until you restart them.

Note This issue may also affect other applications that use the LDAP client.


This issue occurs because the operating system Internet Control Message Protocol (ICMP) encounters a blocking wait for the ICMP response. Then, it makes the LDAP client library asynchronous server response retrieval dysfunctional.


Hotfix information

A supported hotfix is available from Microsoft Support. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing the problem described in this article. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next software update that contains this hotfix.

If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, contact Microsoft Customer Service and Support to obtain the hotfix.

Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, go to the following Microsoft website:

http://support.microsoft.com/contactus/?ws=supportNote The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.


To apply this hotfix, you must have Service Pack 1 for Windows 7 or Windows Server 2008 R2 installed.

Restart requirement

You must restart the computer after you apply this hotfix.

Hotfix replacement information

This hotfix does not replace any previously released hotfix.

File information

For a list of the files that are provided in this update, download theĀ file information for this update 3004383.


To work around this issue, restart all services and worker processes.

Take the Exchange Server issue as an example, you can restart all services and recycle all IIS Worker Processes that are related to Exchange Server.


Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.


Learn about the terminology that Microsoft uses to describe software updates.

Need more help?

Expand your skills
Explore Training
Get new features first
Join Microsoft Insiders

Was this information helpful?

What affected your experience?

Thank you for your feedback!