ORA-12154 from 12.1.0.2.0 client to 11g server - some do, some don't

Windows7/Windows 2012 server:

I installed a database yesterday on an 11.2.0.4.0 server and quickly tested the connection locally and through my notebook's 11g R2 instantclient

doing an SQLPLus user/password@alias (and alias was in TNSNAMES.ORA like

ALIAS=

  (DESCRIPTION =

    (ADDRESS = (PROTOCOL = TCP)(HOST = oracle11g )(PORT = 1521))

    (CONNECT_DATA =

      (SERVER = DEDICATED)

(SERVICE_NAME = ALIAS)

    )

  )

My colleage just sent me an email (I gave him the TNSNAMES.ORA connection data) telling me he got an ORA-12154 when trying to connect.

I tried on another colleague's 12.1.0.2.0 client with the same alias entry and it worked.

Then went to the desktop right next to me, 12.1.0.2.0 client as well, typed in SQLPlus user/password@alias and I'm getting the same ORA-12154.