Personally I find it is a lot easier not to use RealPlayer or HelixPlayer and just install use mplayer and the mplayerplug-in rpm packages instead.
First download and install this;
http://bordeaux.freshrpms.net/rpm.html?id=487
Then use yum;
yum install mplayer mpayerplug-in
Also get the latest mplayer-codec rpm packages from pbone;
http://rpm.pbone.net/
mplayer-codecs-20060611-1.i386.rpm
mplayer-codecs-extra-20060611-1.i386.rpm
After downloading both to a common location as root type something like;
rpm -e realplayer
rpm -Uvh mplayer*.rpm
HTH