seeing as you have a paid for license have you looked up this error on the red hat help database ?
The first thing i do with yum errors is to clean the yum DB
yum clean all
also you can break the update into 3 or 4 parts ( or even just 2 )
i bet that there is a kernel update in there
install that one first
as to cups
what third party repos are installed ?
rpmforge WILL be in conflict with RHN
will output a list of ALL installed repos
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