Solver val error message
 

I have a spreadsheet with some pretty sophiscated financial and statistical
formulas but when I try to save it I get an error message saying "A formula
in a cell (Name:[Spreadsheet Name.xls]Worksheet Name!solver_val) could not be
converted because it contains a function that is not available in the file
format to which you are saving...

My question is how do I figure out which cell is the problem cell so I can
correct the problem? When I faced this problem in the past the precise cell
is given but this error message just says "solver_val" where the cell
location is usually found.

I don't think I ever used the Solver in this worksheet, although I'm certain
I've used it elsewhere in the workbook.

There is no error message or error value in any cell.

Any help is appreciated.