You experience the following symptoms on a computer that is running Windows Vista:
The Allow hybrid sleep option is missing from the Advanced settings tab of the Power Options dialog box in Windows Vista.
When you run the powercfg.exe -a command to list the power states that are supported on the computer, the output that appears includes the following lines:
The system firmware does not support this standby state. Hybrid Sleep
These symptoms occur intermittently. When you restart the computer, the Allow hybrid sleep option reappears. Additionally, when you run the powercfg.exe -a command again, the output that appears includes a line that resembles the following:
The following sleep states are available on this system: Hybrid Sleep
This problem occurs in scenarios where a race condition exists between the Monitor.sys driver and a kernel setting.
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
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.
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.