This is a weird error that has happened to me. Sometimes freecell closes with a directx error. Occurs at random times. Can anyone think of why this would occur? For the life of me, I don't know why freecell is using directx.
Windows Vista and Windows 7 versions of FreeCell use DirectX for simple 3D animations (previous versions did not have such animations). This may be a problem with your video card or drivers. Is the card overheating or damaged? Are your drivers up to date and configured correctly?
Edit: There are reports of FreeCell causing conflicts with games such as Call of Duty: Modern Warfare 2; see this Microsoft Answers post. Since games of this kind often require exclusive access to the video hardware, this may be the issue, especially if the error is "Failed to create DirectX device." Unfortunately, you will probably need to close FreeCell before playing Portal 2; this shouldn't be an issue as current versions of FreeCell can save the game on closing.