glibc 2.1.3-19 fixed a problem where WP Office would not load. When I upgraded to glibc 2.1.3-21, WP Office will not load.
This errata was meant to close serious security bugs, not to fix all the bugs in glibc 2.1.x (there are many). You should use glibc 2.1.9x if glibc 2.1.x does not work (packages in rawhide, will appear in the next Red Hat distribution).
ok, so the serious security bugs were also fixed in glibc-2.1.3-19?
Yes, the security bugs were fixed in -19 already. Anyway, glibc-2.1.92 from 7.0 (or the upcomming 2.1.94 errata) should work as well (ie. have both the security fixes and don't break WP Office).