DFX is now working with my Media Center 13. This may not be exactly related to your problem because my Media Center 13 never crashed, however, this post may help someone else getting DFX going.
Perform the following actions:
Tools>Options>Playback>DSP Ouput format
Click on the word "DFX" first (not the check box) then click in the check box. This worked for me.
If you click the check box only, the DFX field does not highlight and the DFX will not be enabled.