Description of problem: Yum wanted to update the i386 glibc and mozilla packages this morning despite the fact that the x86_64 versions were not available. From my understanding, you want to maintain the same versions of your 32 and 64 bit libs but yum isn't doing this.
Yup, that's the way rpm currently returns archScore(), i386 is compatible with x86_64. The underlying problem is transient, the upstream repo was not yet finished syncing. That's real hard to detect in software ;-)