I can't fix a simple Concatenate formula that won't display it's result
(tried turning Formula Auditting mode on & off).

When I do an "Evaluate Formula" on the cells that formulas are not
displaying values in I get the following
error: The cell currently being evaluated contains a constant".

The formual looks identical to ones in cells above and below (except for
cell #'s that do work fine.
The data referenced  in the formula looks fine.

This one works:

     =CONCATENATE("SHOULDER BOLT ", A6," DIA X ",B6," L X ",H6,)

This one doesn't:
     =CONCATENATE("SHOULDER BOLT ",A12," DIA X ",B12," L X ",H12,)

How can I fix this problem?

Gary