I tried many times to upgrade from Fedora 12 to Fedora 13 with too much fail! I decided to do a fresh install of Fedora 13 in VirtualBox and generate a package list from my Fedora 12 box so I can make it exactly the same.
1. On my Fedora 12 box:
rpm -qa | cut -d – -f 1 > packages.txt
2. Install Fedora 13
3. Copy packages.txt from Fedora 12 to Fedora 13.
4. Copy .repo files in /etc/yum.repos.d from Fedora 12 to Fedora 13.
5. yum install -y –skip-broken `cat packages.txt`
6. Done. =)