problems with internally defined epsg code

[Vincent J. Troisi]

We serve a map from a tiled geotiff of the antarctic continent
from our local server via wms protocols using mapserver.
We have another application that wants to use the map we serve via wms 
protocols.

We have an internally map projection definition and code (3031)
we added to the epsg file for the geotiff file we serve via wms protocols.
When we access the geotiff file
directly from disk there is not a problem displaying the antarctic map in
the mms application.
However, when we try to access the geotiff with the projection of the
added code, we receive information from Mapserver that the epsg
code is invalid. Why is that?
Using the epsg code 4326 the display of the map is not complete;
why is that?

Both applications have access to the locally defined epsg code.

Vince