I haven't come across any .NET errors when using the Grid tool, and I'm not aware of any reports. Perhaps a reinstall or reboot might help?
Regarding your questions/observations, I've been working with development to help answer most of them:
The tool seems to generate new separate 'floor level' models, each containing a 'grid system' cell, for each 'floor level' model. Changes in the Grid Systems dialog triggers an update in the 'grid system' cells, even if the user isn't in the particular model...? [Bentley] This is the intended behavior. If the user clicks the 'Create Grid Models' button, grid models are created (or updated) for all the floors irrespective of whether the active model is the default model.
1. Where does the grid tool get the floor level information from? Floor manager? FM information seems to be stored in the dgnlib pointed to by BB_FLOORMASTER_DGN. Does it also read its own dgnlib for working units, extension, symbology etc? It would be good to have the Grid dialog report the path of Floor Manager dgnlib it is using. Seems out of sync below: [Bentley] Floor and grid information for the grid tool is taken from the dgnlib pointed to by BB_FLOORMASTER_DGN - we don't have a separate dgnlib for the grid tool. Since each project has a single dgnlib pointed to by BB_FLOORMASTER_DGN, there is no need to display the path to that dgnlib.
2. The Grid Dialog should also make clear and list where the 'floor level models' are going to be generated. It appears to be generated in the Design Composition file. Its normal to have multiple design comp files as the job progresses. How do we manage and control this? [Bentley] The floor level grid models are created in the active dgn file.
3. I can see the structural + services having a lot more and different grids. The upper 'Grid Systems Settings' panel should have a tree list column in front of the 'Name' column showing which "BB_FLOORMASTER_DGN" is being worked on, and where the the floor models are being generated as result, ie the design comp files/models? [Bentley] Since the grid models are created in the active dgn file and there is only one floormaster dgnlib for each project, we cannot display a tree list as suggested.
4. What if we need to share grid systems... I can see the structural engineers primary grids being used as the 'backbone' as some point, where both arch + services offset from. Arch's FFL's would be offsets from the structual engineer's SSL's or TOS elevations. Or vice versa in the earlier stages. Cladding outside edge of glass as an offset from the perimeter grids is another example. I think we need to be able to see (..and later link to) multiple "BB_FLOORMASTER_DGN" and Design comps files? Expressions....? [Bentley] Same as question 3 above.
5. Since they are cells, where is the cell insertion point, which I think is being used by the Grid System Settings X,Y offsets, placed? Intersection of the first two gridlines? I think the dialog box needs to make this clear, and graphically display it in the preview window. [Bentley] Good candidate for CR.
5A. The Grid Sysems dialog should be designed to allow bi-directional updates. I can see a lot of people needing to generate the grid, go into the Design Comp model, move and rotate the grid about and then needing to save the revised x,y,z offsets and rotations back to the GS dialog, and only then propagating the changes to the oether floors. [Bentley] Good candidate for CR.
5B. There should be options for alternative 'insertion points', based on grid intersection points which also recognise 'expressions' for offsets, rotations. [Bentley] Good candidate for CR.
6. The grid symbology settings is saved in an xml file pointed to by STRFILE_DRAWINGSETTINGSXML. The Grid Dialog should also list this somewhere. I am sure that the architects and others will want to have their own settings files. Settings for generating the base symbology versus settings for Drawing Rules for resymbolisation should be made clear. [Bentley] Choose Building Designer > Drawing Extraction Manager > Structural Drawing Center, then click the third icon from the left (Open Drawing Settings). From here you can open and save your settings XML file.
7. The grid system display is controlled via the BV panel. I am wondering why this was done. In a 3d view, would the grids be referenced in from the Design Comp model automatically, controlled by the BV button? [Bentley] AFAIK, when an existing DV is applied in the 3D model the grid is handled as annotation.
7A. In a view that is orthogonal to the grids, say an elevation, would the BV system 'resymbolise' the grids to project onto the view even though the grid lines are 'on edge'? [Bentley] It seems so, at least if the grid can be displayed as such.
HTH