sudo not working

[Dave Martini 1]

I want to install an rpm as a regular user. As root I used visudo to 
edit the /etc/sudoers file and added this entry:

martini1        ALL=(root) /bin/rpm

I  then ran this

# :/home/martini1[34]% sudo -l
Password:
User martini1 may run the following commands on this host:
    (root) /bin/rpm

But I can't install an rpm when I do I get this error what am I doing wrong?

# rpm -ivh opera-8.50-20050916.5-shared-qt.i386-en.rpm
error: cannot get exclusive lock on /var/lib/rpm/Packages
error: cannot open Packages index using db3 - Operation not permitted (1)
error: cannot open Packages database in /var/lib/rpm

Thank you.
Dave Martini
LLNL