**This issue has been resolved in ArcGIS 9.3.1 Service Pack 2.**
When displaying a geometric network classes' Flow Direction when the feature class is stored using Oracle's sdo_geometry, the following error displays:
"One or more layers failed to draw:
Underlying DBMS error[ORA-00904: "SHAPE"."LEN": invalid identifier]".
The name of the edge feature class may be appended to the end of the error message. The underlying DBMS error may also be listed several times.
The problem is due to a bug in ArcGIS.