Bug: Datum transformations are not supported when editing
This problem is addressed in ArcGIS 8.1 Service Pack 1. See the Related Information section to download this pack.
When changing the data's coordinate system with a datum transformation set, the edited data jumps.
The datum transformation is not applied properly when converting the data back to the coordinate system of the database.
Make sure that the coordinate systems of the layers and the data frame are using the same geographic coordinate systems (datums).