I've just had a problem on one of my x86_64 boxes with openssl package. I have an 32-bit only application that requires openssl libraries. When I attempted to install openssl.i686 (in addition to already present openssl.x86_64), it failed. The rpm complained about conflicting files (they were all manpages), and I needed to use --force option to install the thing.
The good folks at Red Hat were not able to reproduce it, and I don't have a spare x86_64 box to test it with original RHEL4 myself.
Would be nice if somebody could test installing openssl.i686 (in parallel to openssl.x86_64) on x86_64 box, both under CentOS 4 and under original RHEL4. It could be just something wrong with my installation, or there might be discrepancy between CentOS and RHEL openssl packages.