When you first run "pine" it will ask if you want to run the SIPB
version or the Athena version.  Once you tell it "run this one, and
don't ask me again" it won't ask you again.  However, if you want to
be asked again, to change your pine selection (from SIPB pine to
Athena pine, or vice versa) you need to delete the file in your home
directory named .athena-pine-noask.  

Depending on which one you said you wanted to use, you will have
either a file called .athena-pine-noask  ("I want to use Athena pine")
or .athena-sipb-pine-noask ("I want to use SIPB pine"). 

To remove either, at the Athena prompt type:

athena% rm ~/.athena*pine-noask

The next time you run pine, you will see a menu prompting you to select
which pine version you want to use.

Athena pine is the new offical version of pine on Athena and SIPB pine is
likely to become unsupported in the future, so use SIPB pine at your own
risk.