PROBLEM

This error may occur if you try to open a Relux project by double-clicking.

Then this message will appear: "An error occurred when the command was passed to the program".
 
WHAT IS CAUSING THIS
This error may also occur with other files from AutoCAD and Microsoft Office.
According to Microsoft, this is a so-called DDE error, basically a communication problem between the programs.

SOLUTION
If you first open Relux or the corresponding program and out the files, the error does not occur.

This error message does not appear when you select the corresponding file in the folder and select the "Open" option from the right mouse button.