Jason Tsang has details of the updates coming down from Windows Update for Vista Media Center (KB967632) and Vista with TV Pack (KB966315)

[UPDATE: The KB pages are up now and there have been some minor changes, thanks to peterfnet]

June 2009 Cumulative Update for Media Center for Windows Vista (KB967632)

• Fixes an issue where closed captioning will turn off when the focus changes from Live TV playback
• Fixes an issue where sometimes during Live TV playback, a blank blue bar would be displayed on the screen
• Increases the number of tiles that are supported on the top level of the Media Center start menu
• Fixes a top Watson crash issue
• Fixes a Windows Media Center TV Guide issue that is related to the digital TV switchover

The update replaces the previous cumulative updates

Download Links:

• June 2009 Cumulative Update for Media Center for Windows Vista, 32-bit versions
• June 2009 Cumulative Update for Media Center for Windows Vista, 64-bit versions

June 2009 Cumulative Update for Media Center TV Pack for Windows Vista (KB966315)

• Issue in which a blank blue bar may appear on the screen during the Live TV playback.
• Issue with Media Center parental controls and Windows Media Player on Windows Vista x64-based systems.
• Issue in which black screen may appear when you play DVD.
• Increases number of tiles supported on the top level of the Media Center start menu.
• Issue in which the seek bar is not displayed correctly on some Media Center extensibility applications.

Download Links:

• June 2009 Cumulative Update for Media Center TV Pack for Windows Vista, 32-bit versions
• June 2009 Cumulative Update for Media Center TV Pack for Windows Vista, 64-bit versions