Here is the error i get by running a "sqlplus -v" after installing an oracle client 10.2.0.5 on an AIX 5.3.9 server.
Could not load program sqlplus:
Symbol resolution failed for sqlplus because:
Symbol __pthread (number 307) is not exported from dependent
module /usr/lib/libpthreads.a[shr_xpg5_64.o].
Examine .loader section symbols with the 'dump -Tv' command.
Seems like an environment problem, but I forget, what is the library path in AIX, like LD_LIBRARY_PATH on Solaris. Might be finding no or wrong library files in dynamic link. You might run 'ldd -rsv sqlplus' and see where it is getting libs, or not.