Art,
I couldn't understand if you finally used the "ASEL-AATT" method or if you refer to the menu-method. Does ANSYS write some warning or error message in the output window when you try to select the areas? Or even with the command-line method, after issueing "ALIST,all" (warning: first use ASEL to limit selection to the areas you need, otherwise use "ALIST,area-min-number,area-max-number") you can see that the material assignment is wrong?
When you make a global assignment for elem type, this goes to all appliable entities in the database (for ex., if you give default elem type to PLANE42, lines will obviously not be affected), but you can still override this by making specific assignments, just like with the command you want to use. This should not affect material assignment, though...
You can also do that:
1- mesh with all areas using the same material
2- issue ASEL,s,area-num for the first area you want to modify (or ASEL,s,a-min,a-max for a sequence), or CMSEL,s,component-name if you have defined components made of the areas of the same type. The equivalent menu is Utility Menu -> Select -> Entities -> Areas -> ... or Select -> Select Components -> by name ...
3- issue ESLA,s to select all elements attached to the selected area(s). The equivalent menu is Select -> Entities -> Elements -> Attached to - Areas - From full
4- issue EMODIF,all,MAT,mat-number. The equivalent menu is Modeling -> Move/MOdify -> Elements -> Modify attrib -> pick all (as you already selected those you want to modify)-> Material.
This method DOESN'T change material default attribution to the AREAS themselves, but only to the ELEMENTS attached to the area. That means that, if for some reason you have to clear the area mesh and remake it, you will have to pay attention once again to elem / material attributes !!
Let me know if it works for you... BTW: which version of ANSYS are you using? Commands always remain the same, but menu paths not always... I'm presently refering to v. 7.0 / 8.0
Claudio