No experience with .x files so this just a guess. And I assume that this is what you are doing :
1. you create a circle with hole in AC3D
2. create a triangle in AC3D
3. export the file containing the 2 pieces in .x format
4. load that file into your program.
If the above is correct, open the hierarchy window (Tools-->Hierarchy View) and move the triangle to the top of the list of objects (right click on triangle object in the hierarchy window -->move to head).
Now export the file ... see what happens. No idea if it will help ... just a guess that the position in the hierarchy (the order of objects) in the .x file maybe important.
griff