Microsoft released two reliability updates for Windows Media Center for all editions of windows 7 OS.These updates are intended resolve liability issues such as Windows Media Center displaying Low Bit Rate overlay messages and fixes some problems in
TV tuner functionality.

Update to the TV tuner functionality (KB981129):

This update fixes a deadlock issue that occurs when you use a TV tuner in Windows Media Center. This issue may occur if you change channels fast and frequently (also known as “channel surfing”), in Windows Media Center.

Download the update KB981129:
KB981129 for 32-bit (x86) Windows 7
KB981129 for 64-bit (x64) Windows 7

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Fixes for the Windows Media center Low Bit Rate overlay messages(KB981130):

Windows Media Center monitors the incoming bit rate of live TV. Without this monitoring, the bit rate drops very low when the analog TV input is weak or does not have a signal. This causes a black screen or a static screen to be displayed.

However, the method that is used to monitor the incoming bit rate on analog signals is too sensitive. This may cause a false detection of a low bit rate.Install this update if you see low bit rate message on Windows 7 Media Center when watching live TV.

Download the update KB981130:
KB981130 for 32-bit (x86) Windows 7
KB981130 for 64-bit (x64) Windows 7