I have resolved my own question. At issue was the fact that I had a 32-bit library installed, but not the 64-bit version. Yum did the trick: yum install compat-libstdc++-33.x86_64   -M     When I attempt to start IDL's online help assistant I get this message: IDL> ?atan       % ONLINE_HELP: Starting the IDL online help assistant. /usr/local/itt/idl64/bin/bin.linux.x86_64/idl_assistant: error while loading shared libraries: libstdc++.so.5: cannot open shared object file: No such file or directory However the library in question is installed: # rpm -qil compat-libstdc++-33-3.2.3-63.i386 Name        : compat-libstdc++-33          Relocations: (not relocatable) Version     : 3.2.3                             Vendor: Fedora Project Release     : 63                            Build Date: Thu 21 Feb 2008 06:53:10 PM PST Install Date: Fri 14 Nov 2008 08:25:51 PM PST      Build Host: xenbuilder4.fedora.phx.redhat.com Group       : System Environment/Libraries   Source RPM: compat-gcc-32-3.2.3-63.src.rpm Size        : 733132                           License: GPL Signature   : DSA/SHA1, Thu 10 Apr 2008 06:48:53 AM PDT, Key ID b44269d04f2a6fd2 Packager    : Fedora Project URL         : http://gcc.gnu.org Summary     : Compatibility standard C++ libraries Description : The compat-libstdc++ package contains compatibility standard C++ library from GCC 3.3.4. /usr/lib/libstdc++.so.5 /usr/lib/libstdc++.so.5.0.7 # ls -l /usr/lib/libstdc++.so.5* lrwxrwxrwx 1 root root     18 2008-11-14 20:25 /usr/lib/libstdc++.so.5 -> libstdc++.so.5.0.7* -rwxr-xr-x 1 root root 733132 2008-02-21 18:53 /usr/lib/libstdc++.so.5.0.7* I am running Version 6.4 (linux x86_64 m64).   Any pointers would be greatly appreciated.   Regards, Mark