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Quite some time ago, when Vista just went RTM, Risk Strahl discovered that when he used Microsoft Wireless Laser Mouse, code intellisense and markup validation in Visual Studio stopped working. Since several activities in VS are done in a background on idle (not to be confused with background threads - idle processing is performed on the main thread), it was clear that VS was not getting any idle time slots, i.e. something was keeping OS busy. We tracked the issue down some third party applications as well as to a bug in Microsoft Wireless Mouse driver that was keeping OS busy and prevented OS from going to sleep or launching screen saver. See Knowledge Base topic for details and workarounds/updates. What about Windows 7? The fix was included in later builds of client OS, i.e. change is in Windows 7, but it is not included in Windows 2008 Server. If you are using Windows 2008 Server as your development machine and you have wireless mouse, make sure you install latest Intellipoint drivers.