RH9: Installing New RPMs

[geno <geno pop net>]

Often when I double-click on an RPM ( downloaded from RHN or other 
RH9-specific list) to start installation, I get a very brief message, but 
nothing else happens.  The message says: Processing system update...package 
dependencies must be determined....Processing Headers.  I get the same 
result whether or not I first remove the prior version.

What am I doing wrong?

Thanks.

geno