Seems like an invalid parameter or parameter name...
Can You remember which parameters should be there? If yes, try a note showing these parameters one by one and look for irregularities.
What if You use parameters somewhere else, e.g. in the search dialog, a family table, etc.? Can You open the relations window?
Try to switch to the old parameter ui: set the option new_parameter_ui to no.
Then open the parameter dialog, make your changes, save and try to switch back to the new ui.
Ken,
What about the Relations dialog (Tools > Relations)? Can you open that? If so, what happens when you expand the Local Parameters in the lower portion of the dialog?
Also, how about adding the Model Params to the model tree (Settings > Tree Columns)? You will be able to see all the parameters and edit their values if necessary.
Ron Thellen