[Evolution] Problem installing 1.5.6 RPM snapshots in Mandrake

[Andrew Conkling <andrewski verizon net>]

I'm trying to install the 200404121814 snapshots of Evolution 1.5.6 on my 
Mandrake 10.0 machine. I know the RPMs are for 9.2; that shouldn't cause any 
problems. (I successfully installed 1.5.5 last week.) However, when 
installing the libgtkhtml3.1_7-3.1.11.0.200404121814-0.snap.ximian.7.1.i586.rpm 
package, I get the following error:

root:evo1.5.6$ urpmi libgtkhtml3.1_7-3.1.11.0.200404121814-0.snap.ximian.7.1.
i586.rpm
unable to register rpm file
Everything already installed

I googled around and could find nothing pertinent. I also thought that mayhap 
the RPM was corrupted, but the size matches that listed on the ftp mirror. Can 
anyone help as to why I'm getting this error?