When you configure Windows Media Player 12 to display subtitles on Windows 7, the video experience may not be enjoyable as video image flickers every time that a new line of subtitle is displayed. Microsoft has confirmed this issued and posted hotfix for this.
This problem occurs because of an issue in the way that the Enhanced Video Renderer (EVR) handles subtitle notifications. The hotfix applies to Windows 7 & Windows Server 2008.
Download Fix291755 for Windows 7 WMP 12 Video Flickering issue.