I know you never read the Readme file. Here is part of what it says.
Working with Previous Versions
- Using the new Display Themes object will create proxy objects when opened in previous versions of Architectural Desktop.
- The new Gross and Usable profiles for spaces are not supported in previous releases. Enabling and using this feature in Architectural Desktop 2006 will result in spaces only displaying the Net boundary in previous versions, as this was all that was available in previous versions.
- The new mask option for Break Mark Tool is not supported in previous releases. Using this feature in Architectural Desktop 2006 will result in Break marks only displaying the cut line and not the masked area in previous versions of Architectural Desktop.
- An additional display representation was added in ADT 2006: “Anchor Extended Tag to Entity” for schedule tags using the constrain option. Since this display representation is not present in prior versions of ADT, the representation will show up as proxy in these versions.
- Uninstall of ADT 2004 after ADT 2006 has been installed will break Tool Palettes in this version. Running a Repair Registry will restore proper operation.
- Database Field Codes values are cached but will not update in previous versions of ADT or AutoCAD.