Unable to connect after moving the Oracle database from one Unix to another. (4260389)

We recently moved from one UNIX box to another. Since the move, I have been unable to connect. I have changed my tnsnames.ora file to reflect the new server name and I can connect to it using SQL + fine, but when I try to connect now using SQL Nav I get this message:

ora-12505: TNS: listener could not resolve SID given in connect descriptor.
Make sure connection parameters are correct and try again.

I had my DBA put the db back up on the old Unix box, and I can connect to it without changing my tnsnames.ora file back to the old server. Why? I removed my old connections to this db from my workspace. I then tried copying the tnsnames.ora file from a co-worker who can connect to this database on top of my own nad I still cant connect. Nav works for all my other database, except this one whose location was recently changed