are you sure that your upgrading (not installing) the new package. try the following command and post the output here.
Code:
$ rpm -Uvh <gtkpackagename.rpm>
for installing mplayer download the packages from
www.mplayerhq.hu. Yo'll need the following packages essentially.
1. mplayer
2. mplayer-codecs
3. mplayer-gui
4. mplayer-skin-default
download the above packages and install it using the following command
Code:
$ rpm -ivh mplayer*
And next time post gnu/linux related queries in Open Source section.