I had a similar issue and had to make some minor adjustments when converting from v10 to Autocad 2006. In addtion on the AutoCAD side make sure that when you are inserting the block it is not scaled to "unitless". Set scale factor that was defined in the Translator setup file in Archicad so that inches=inches, meter=meter, etc.
As per the help section on importing/translation:
Drawing Unit
As you export or import something in DXF or DWG, you must set the size and distance conversion factor to ensure that ArchiCAD interprets the data correctly. The user interface of the DXF/DWG Drawing Unit consists of a pop-up list and a numeric data field. The pop-up list has four items for standard drawing units (1 meter, 1 millimeter, 1 inch, 1 foot).
Two custom units are also available: Custom [mm] and Custom [inch]. Selecting either of these gives you a field in which you enter numeric data according to your needs.
When opening a DXF/DWG file, you must define a scale at which you would like to see the correct ratios of elements drawn in AutoCAD. This particularly applies to arrowheads, symbol line types and symbol fills.
Set Scale Factor: Choose one of the three options:
• Set scale factor separately with each conversion: In this case, a dialog box appears after clicking the Open button, letting you set the desired scale factor.
You may click the arrow before the text ‘Show Example’ to display an explanation of the effect of the scale factor:
This scale factor has an effect on Texts and Arrowheads of the imported AutoCAD drawing. Click OK to accept the scale factor. • Use constant factor for all conversions: Set a scale factor for ArchiCAD to use for these conversions. In this case the Scale Factor Dialog will not come up.
• Always use the scale set in the currently active ArchiCAD window: The scale of the ArchiCAD Floor Plan will be used for conversion. This is the same method which worked in ArchiCAD versions up to 8.1.
Note: If you used the Set scale factor separately with each conversion option, the Scale Factor Dialog will also come up in case an AutoCAD drawing is dragged and dropped onto the ArchiCAD Window background (drag-and-drop Open), and in case an AutoCAD drawing is merged into the ArchiCAD Floor Plan, a Section/Elevation Window or a Detail Window (drag-and-drop merge)
