When exporting a .DXF file from CorelDRAW 11, it gives you the option to select the type of AutoCAD file you want (2000, 13, 11, etc).
When exporting your .DXF file from CorelDRAW 11 to use in Wilcom ES, select AutoCAD file 11. This will allow the .DXF file to be used in Wilcom ES.