[CentOS] cannot install glibc.i686 on x86_64

I cannot install glibc.i686 on a x86_64 system because I get 

Error: Missing Dependency: glibc-common = 2.5-81 is needed by package 
glibc-2.5-81.i686 (base)

glibc-common.x86_64 is installed, but it's apparently looking for i686.
There's indeed no glibc-common for i686.
There's also glibc.i386 and glibc-common.i386 available, but I think I 
don't need them.

I have other x86_64 systems that have an installed glibc.i686 and no 
glibc.i386 and glibc-common.i386. I don't remember how I did that, 
probably on first install.

How do I get glibc.i686 with yum on the system?


Kai