Measuring tool precision / units (SW2009)

The measure tool is only showing two units precision (SW2009 SP 5.0 Win XP x64). When I try to change the precision from two to three units or more, I receive the error message "Please enter an integer between 2 and 256" which is what I am doing when I type in 3 units. I do not remember this being an issue in SW2007.

Why is it set to 2 units anyway, and how to I get this to work? I suspect it is either a bug in SW2009, or a document properties setting.

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