duplicate packages installed

[Margaret Doll]

In one of my RedHat systems I seem to have many packages installed  
twice.

Partial output from "rpm -aq"

alsa-lib-1.0.17-1.el5
alsa-lib-1.0.17-1.el5
alsa-utils-1.0.17-1.el5
amtu-1.0.6-1.el5
anacron-2.3-45.el5
antlr-2.7.6-4jpp.2
apr-1.2.7-11.el5_3.1
apr-1.2.7-11.el5_3.1
apr-util-1.2.7-7.el5_3.2
apr-util-1.2.7-7.el5_3.2
arptables_jf-0.0.8-8
arpwatch-2.1a13-21.el5
aspell-0.60.3-7.1
aspell-0.60.3-7.1
aspell-en-6.0-2.1

How do I get rid of the duplications?  I am running 2.6.18-128.1.14.el5.