Troubleshooting with Event Viewer
To discover what could be causing your issue, check the Event Viewer. To access it in Windows Vista, click on the START button and to the Control Panel. Depending on how you have the view (either classic or Vista), you will either select Administrative Tools (classic view) or System and Maintenance. In System, click the 'view logs' link under Administrative Tools.
Alternatively, you can type in 'event viewer' in the search bar within the START Menu.
Within the Event Viewer, click the Applications and Services folder and the Windows folder. Go through and find any service that has a red X, along with the word 'error'. Look for the events that happened around the time that you first received the error. One of the biggest issues was that of Windows Vista and Norton's Security. When a user uninstalled Norton's, sometimes files and folders from the software did not get uninstalled and it can cause issues with the Windows built-in firewall and it's Defender application (now known as Security Essentials).
The remedy for this is to make sure that your Norton software is completely uninstalled. There are a variety of program removers such a Revo Uninstaller and CCleaner that do a very good job of making sure programs completely remove themselves from the system. These and other can be found at Download.com.
Other issues included the ATI Catalyst center for ATI graphics cards, bad driver installs, thumb drives, and card readers. The best way to avoid this error message is to make sure that your applications and software are updated for Vista and that Windows Vista itself is updated to the latest version of its security pack.