Failed install of freeradius2-2.1.6-2.el5.i386

Today I tried to install freeradius2-2.1.6-2.el5.i386 and ran into a dependencies problem I could not solve. After downloading support for SQL and all required dependencies I started my install and got this message - Missing libltdl.so.3. I am running Linux rhel 2.6.18-8.el5 and wonder now where on my software disks (I have searched) is this file? Is this file part of some other software required to run freeradius2-2.1.6-2.el5.i386? Suggestions ? Thanks Steven -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean.