Personally, im guessing your using Maya Personal Learning Edition. Correct me if i'm wrong but this can't export to .x format, and if you had managed to get it to work then it would be against the license agreement.
If you have a full version of Maya, either Complete or Unlimited, then this functionality should be built in. Here is a quote off of the Maya website:
Quote: "Features
Import/Export Options
Enhanced or new data support formats in Maya facilitate the accurate transfer of data between Maya and other applications. Whether bringing models into Maya for design visualization or exporting Maya data to other software packages, you will get the most value from your digital assets. Supported file formats include Macromedia® Flash, Adobe® Illustrator®, Encapsulated PostScript®, Scalable Vector Graphics, DXF, IGES, OpenFlight®, StudioTools® and OBJ, DDS, PNG, STL, and DirectConnect for SolidWorks®."
If this functionality is not built in then i will have to seriously reconsider my decision to purchase the academic version of Maya Complete at the end of the month. If you are a student then you can purchase this version for around £210 in the UK from:
http://www.journeyedeurope.com/
Hope this helps,
Mike
*** Formerly Code Monkey ***