When, somehow, the same RPM is installed twice, "rpm -qa" shows two identical instances. "rpm --rebuilddb" in the recent past was able to eliminate one of the duplicate database entries; rpm-4.0-4 no longer seems to be able to. This leaves as the only recovery method the complete uninstallation of the program ("rpm -e --allmatches") followed by a reinstallation. It may help to know that the host displaying this problem is "up2date" with all glibc/rpm/etc. patches as of 2000-12-25 or so.
Um, removing duplicates during --rebuilddb was never "supported" functionality, only a dirty hack to work around a buggy development rpm that leaked through Raw Hide. In fact, rpm is designed to be perfectly happy with multiple instances of the same package installed (and in the database). Add --define '_filterdbdups 1' if you must, or (equivalently) mkdir -p /etc/rpm echo "%_filterdbdups 1" >> /etc/rpm/macros but I suggest that you really need to look at how the duplicates are getting in the database in the 1st place, as that's where the real problem is.