[CentOS] Yum update conflicts perl-Math-BigInt

I followed the Wiki instructions for setting up *yum-priorities*.
I added the rpmforge repo
I installed clamd without a problem.
Now when I go to update I get conflicts with perl-Math-BigInt.

Is the only solution to uninstall the base version and then install the 
rpmforge version?

According the the wiki
"Packages from repositories with a lower priority will never be used to 
upgrade packages that were installed from a repository
with a higher priority."
If this true why the conflicts? please advise
Thanks
Dan