[OS X Emacs] ediff-buffers does not fill in the buffer A and buffer B names

[Kalash]

When I use command line emacs (/usr/bin/emacs) on OS X and issue a 
ediff-buffers with at least two  buffers open, I get the following prompts:
Buffer A to compare (default a.c): 
Pressing a return selects the indicated default buffer as buffer A for diff.
Similar prompt is displayed for 
buffer :
Buffer B to compare (default b.c):'
Again, pressing a return selects the indicated default buffer as buffer B.
I have seen this similar behavior on Linux (Ubuntu and RHEL).
 
However, when I use Aquamacs v1.9, I do not get any default buffer name 
displayed neither for buffer A nor for buffer B. This is on a Snow Leopard 
system.

Any help in pointing out any customization to be set up correctly would be 
welcome.

TIA.
Kalash