Having upgraded to the latest version of MicrocodeStudio and MicroCode Loader i have got rid of that problem.

But still:
If I look at the the EEPROM Data in the HEX-File using any other Tool than MPLAB or MCLoader (ie. IC-Prog) I see "garbage"
(I'm using different Programmers for different purposes, IC-Prog is just an example)

The strange thing is:

When I program a device using the Loader and read it back (ie. in IC-Prog) everything looks ok.

To me it looks like MPASM is handling / structuring EEPROM Data for the 18F in some different way than it does for the 16F devices.
when I compile exactly the same Code for a 16F876 the EEPROM Data is ok (even in IC-Prog).

So some newer programming tools appear to take care of the issue.

Does anyone have a final word of clarification ?

rgds.