Upgrading Fedora is pretty safe most of the times. This one time I had issues with the openssl package having a change that wasnt compatible with x2go.
Since I use x2go all the time I wanted to pin the version of openssl to libssh-0.5.5-1.fc20.
yum install yum-plugin-versionlock yum versionlock libssh
And that was it! The problem was later resolved upstream, and then you use yum versionlock clear, to remove the lock.