We seem to have this problem with some of our users and I'm stumped. I just upgraded to 4.1.4 the other day, though this issue was occurring on 4.1.3 as well.
When I lookup a user in the GAL, I can see all the contact info - home number, office number, fax, e-mail and PIN.
Some of our other users, on a different Exchange server, looking up the same user will see only the fax an e-mail.
We all have the same CDOs and MAPIs and this happens quite often. I'm going to contact TSupport, but I always check this site first.