Data validation drop downs don't recognize dynamic named range
 

I've set up a worksheet where row 2 contains column titles and data
validation.
Below this is are the data entry cells with validation lists based on column
title.
The validation lists are named ranges on another sheet called Tables. I get
proper drop downs.

When I change a name reference to
"=OFFSET(Tables!$B$2,0,0,COUNTA(Tables!$B:$B)-1,1)" I no longer get the drop
down. When I try to GoTo the named range it doesn't show on the GoTo list.
Formulas like "=CountA(Media)" work correctly.

Any help would be appreciated.

Glen