question about 2 versions and libraries

Hello List,
i have version 7.1.3 (debian package) and version 7.2.1 (compiled from
source) an the same box.
both versions (server and client programs) use the libs from the debian
installation.
i found a few postings with this topic and there is said to set
LD_LIBRARY_PATH to the correct lib path.
i did this but still the libs from the debian installation are used
(despite of libpg.so.2):

arwen:~# set |grep LD
LD_LIBRARY_PATH=/usr/local/postgresql7.2.1/lib
arwen:~# ldd /usr/local/postgresql7.2.1/bin/psql
       libpq.so.2 => /usr/local/postgresql7.2.1/lib/libpq.so.2 (0x40016000)
       libcrypt.so.1 => /lib/libcrypt.so.1 (0x400d8000)
       libresolv.so.2 => /lib/libresolv.so.2 (0x40105000)
       libnsl.so.1 => /lib/libnsl.so.1 (0x40117000)
       libdl.so.2 => /lib/libdl.so.2 (0x4012c000)
       libm.so.6 => /lib/libm.so.6 (0x40130000)
       libreadline.so.4 => /lib/libreadline.so.4 (0x40152000)
       libc.so.6 => /lib/libc.so.6 (0x40178000)
       libncurses.so.5 => /lib/libncurses.so.5 (0x4029b000)
       /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
arwen:~#

and another problem is arising with LD_LIBRARY_PATH set
(unix_socket_directory is set to /var/run/postgresql in postgresql.conf):

arwen:~# /usr/local/postgresql7.2.1/bin/psql -p 6543 template1
psql: could not connect to server: No such file or directory
       Is the server running locally and accepting
       connections on Unix domain socket "/tmp/.s.PGSQL.6543"?
arwen:~#

Any hints??

Regards
Tina

ps: i am not getting mails from the list since yesterday , are there any
problems?