I'm not sure about this but that seems like a bug when it thinks that the 310 driver package is an upgrade for the 304 driver package.
Jan 23 21:43:39 Updated: kmod-nvidia-310.32-1.el6.elrepo.i686 Jan 23 21:43:49 Updated: nvidia-x11-drv-310.32-1.el6.elrepo.i686 Jan 24 00:43:58 Installed: kmod-nvidia-310.19-2.el6.elrepo.i686 Jan 24 00:44:10 Installed: nvidia-x11-drv-310.19-2.el6.elrepo.i686 Jan 24 00:59:38 Installed: kmod-nvidia-304.64-1.el6.elrepo.i686 Jan 24 00:59:49 Installed: nvidia-x11-drv-304.64-1.el6.elrepo.i686
This doesn't appear to be a CentOS issue, possibly an elrepo issue.
Barry