[syslog-ng] Cannot start syslog-ng-3.3.1

Hello I installed syslog-ng-3.3.1 from source on debian lenny. And when I start it, it says "error while loading shared librairies: libsyslog-ng-3.3.1.so: cannot open shared object file: No such file or directory" though this file is in /usr/local/syslog-ng/lib/ libsyslog-ng-3.3.1.so Anyone can help?