The underscores indicate that this is a macro (ie. it is being called by from another library part). It is possible that some setting was changed in the main part that is passing the bad value. This can be hard to track down since, while you can open the macro to check the code etc., this doesn't necessarily help and it can be difficult to tell which window (presumably it is a window) is calling the macro.
There are two fairly quick ways that may find the source of the problem. One is to look at the 3D view for missing parts. The other is to model parts of the building to zero in on where the error occurs (first half, then one quarter, an eighth, etc. until you've found it. Make sure that the you have the report option turned on in the imaging preferences in your work environment (and turn off the "Interrupt with Error Messages" if you haven't already).
