Data Grid Array to Scalar Error

[Ray]

Has anybody seen this:

       An error has occurred in behavior for the column template:
       add: can't add array to scalar

I'm not sure what this means.  Other than the error popping up it 
doesn't seem to be doing any harm.  I've tried putting the handler which 
causes the error in a try-catch.  This works well but I can't save the 
RevDataGridLibrary stack so I have to re-do it each time I open the stack.

Any ideas?