After you set the value of the EventMask parameter to WTS_EVENT_FLUSH in the WTSWaitSystemEvent function, no pending calls to the function return on a Windows Vista-based computer

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On a Windows Vista-based computer, you develop an application by using the WTSWaitSystemEvent function. When you set the value of the EventMask parameter to WTS_EVENT_FLUSH, all pending WTSWaitSystemEvent function calls on the specified terminal server handle are returned. However, no pending calls to the WTSWaitSystemEvent function return as expected.

Note This problem does not occur on a Windows XP Service Pack 2 (SP2)-based computer.

Service pack information

To resolve this problem, obtain the latest service pack for Windows Vista. For more information, click the following article number to view the article in the Microsoft Knowledge Base:
935791 How to obtain the latest Windows Vista service pack

Hotfix information

A supported hotfix is available from Microsoft. 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 this specific problem. 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, visit the following Microsoft Web site: Note 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.


No prerequisites are required.

Restart requirement

You have to restart the computer after you apply this hotfix.

Hotfix replacement information

This hotfix does not replace any other previously released hotfixes.

Registry information

To use this hotfix, you do not have to make any changes to the registry.

File information

The English version of this hotfix has the file attributes (or later file attributes) that are listed in the following table. The dates and times for these files are listed in Coordinated Universal Time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time item in Control Panel.
Windows Vista, 32-bit versions
File nameFile versionFile sizeDateTimePlatform
Update.mumNot Applicable2,01921-Aug-200712:20Not Applicable
X86_5d9b844bb56e83ca8d5ea19680f64c4e_31bf3856ad364e35_6.0.6000.20664_none_0b64d8c076787341.manifestNot Applicable71221-Aug-200712:20Not Applicable
X86_microsoft-windows-t..nalservices-runtime_31bf3856ad364e35_6.0.6000.20664_none_db466d43e82504af.manifestNot Applicable6,56321-Aug-200712:20Not Applicable
Windows Vista, 64-bit versions
File nameFile versionFile sizeDateTimePlatform
Amd64_5d9b844bb56e83ca8d5ea19680f64c4e_31bf3856ad364e35_6.0.6000.20664_none_678374442ed5e477.manifestNot Applicable71421-Aug-200712:20Not Applicable
Amd64_ff73221e92fa13c996b100208a38d5b5_31bf3856ad364e35_6.0.6000.20664_none_cf79b4d693e694c1.manifestNot Applicable71621-Aug-200712:20Not Applicable
Amd64_microsoft-windows-t..nalservices-runtime_31bf3856ad364e35_6.0.6000.20664_none_376508c7a08275e5.manifestNot Applicable6,58521-Aug-200712:26Not Applicable
Package_1_for_kb941561~31bf3856ad364e35~amd64~~ Applicable1,81121-Aug-200712:20Not Applicable
Package_2_for_kb941561~31bf3856ad364e35~amd64~~ Applicable2,03021-Aug-200712:20Not Applicable
Update.mumNot Applicable1,92521-Aug-200712:20Not Applicable
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section. This problem was first corrected in Windows Vista Service Pack 1.
More information
For more information about the WTSWaitSystemEvent function, visit the following Microsoft Web site: For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base:
824684 Description of the standard terminology that is used to describe Microsoft software updates
WTSWaitSystemEvent, WTS_EVENT_FLUSH, Vista

Article ID: 941561 - Last Review: 01/16/2015 10:03:27 - Revision: 4.0

Windows Vista Enterprise 64-bit Edition, Windows Vista Home Premium 64-bit Edition, Windows Vista Ultimate 64-bit Edition, Windows Vista Business, Windows Vista Business 64-bit Edition, Windows Vista Enterprise, Windows Vista Home Premium, Windows Vista Ultimate

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