After upgrading to OS X Lion most of my software was working fine. But, alas, the first time I used Oracle sqlplus (for all my Oracle scripting goodies) it died with a segment fault.
I did have a full 10.2.0.4 client installed so I tried the 64 bit instantclient and got basically the same problem.
I then tried the 32 bit instantclient and after doing some mods to key Oracle environment variables in /etc/bashrc I got it finally to work.
The variables in bashrc were set by the Oracle client installation (as it does on almost all platforms) are the main Oracle ones: ORACLE_HOME, LD_LIBRARY_PATH, SQLPATH, DYTD_LIBRARY_PATH and TNS_ADMIN. All of these I set to the instantclient directory - you will need a tnsnames.ora and/or sqlnet.ora as well for the Oracle Network connection strings.
Hope this helps and good luck.