Anybody got a working Zimbra on RHEL6?

I got this error even if libstdc++ for x86_64 is already installed.
Checking for prerequisites...
FOUND: NPTL
FOUND: sudo-1.7.2p2-9
FOUND: libidn-1.18-2
FOUND: gmp-4.3.1-7
MISSING: /usr/lib/libstdc++.so.6
Checking for suggested prerequisites...
FOUND: sysstat
###ERROR###


But when I tried to install the i686 version, this is what I got
Checking for prerequisites...
FOUND: NPTL
FOUND: sudo-1.7.2p2-9
FOUND: libidn-1.18-2
FOUND: gmp-4.3.1-7
FOUND: /usr/lib/libstdc++.so.6
Checking for suggested prerequisites...
FOUND: sysstat
Prerequisite check complete.

Checking for installable packages

Found zimbra-core
Error: attempting to install i386 packages on a x86_64 OS.
Exiting...


it does seem to recognized the libstdc version for i686 but somehow the system got confuse. Why can't Zimbra recognized the installed libstdc? Any idea how to fix this? Thanks.