I am getting the exact same error message.  In my case, the user is choosing a date from a datepicker in a grid and then clicking off the row in the grid.  I am running the latest Infragistics code (19.1) so if this was fixed previously, I should have that fix already.

I have a handler for the InitializeRow event of the grid and some of my grids have a lot of rows and/or columns.  We have found that looping through the column collection of the grid band slows things down because it creates an instance of the column object.  We were told we could improve performance by trying to avoid creating this instance until the last possible moment.  As a result, I am looping through a separate collection of the keys in the column collection and when I need to finally get an instance of the column, I create the instance of the column object by using Row.Cells(strKey), where Row is the grid row.  To avoid errors, I am first checking to see if the column exists.  What I have settled on in the meantime is putting a TRY…CATCH block around this call and leaving the EXISTS check out.  This seems to be working pretty well for me, but I was hoping to find a better way.

I misspoke.  My code will get a cell and I can get the column from that cell.  Just wondering if there is a better way to do this.  Sounds like EXISTS is the way to go?