You sent me an email with a screenshot and it appears that your Inventory Lookup has been replaced with a Bin Locations lookup.  Was somebody in Queries - SU-A editing the grids?  
 
If you have not edited the grids to any extent and want to restore back to the original, go to Queried - SU-D and choose overwrite and the original standard IS Tech grids will replace your current ones.
 
If you have edited other grids and want to keep the other modified grids, then use SU-A and delete the INVENTORY grid (which is now pointing to the wrong file) and then SU-D and choose  Skip and it will bring in anything that is not in your grid but is in the standard (which would include Inventory since you deleted it) but leave the others alone.