It seems RH6'2 db1-devel and db2-devel packages conflict with glibc-devel. In upgrade operations, glibc-devel isn't upgraded even though the rest of glibc is to a newer version. This might cause interesting problems for people compiling their own stuff.
This happens with 6.2 -> beta2 too. As the upgrade path is the focus in beta2, severity/priority has been increased.
*** Bug 13328 has been marked as a duplicate of this bug. ***
Fixed in beta3.