Fedora 20 don't boot to desktop
Since an update, my Fedora don't want to boot to desktop, i've tried with all kernel. I can access a tty and connect to my user in it. I've tried to run yum update again, but I got many dependency problem with the nvidia driver from RPM Fusion (I'm using akmod). Running yum update --skip-broken is omitting glibc-headers and kernel-headers, but even with --skip-broken the update don't finish. I've tried updating using --enablerepo=updates-testing, but it don't work too.
I'm currently using akmod-nvidia on F20 and am not having any dependency issues. Do you have any third-party repos other than rpmfusion, or updates-testing packages that might be causing the problem?
I only have RPM Fusion and default Fedora repo enabled and I've got the problem before enabling updates-testing.
You could try running "yum list extras" to see if you have any packages installed that are not currently available in your enabled repos (other than packages which can have more than one version installed, like old kernels, which are expected). I can't think of anything else - AFAIK, there are currently no actual dependency problems between Fedora stable and rpmfusion.
Edit: You could also try "package-cleanup --problems" and "package-cleanup --dupes" to look for existing problems with your installed package set.
You might also have to make sure you have the right version of akmod-nvidia installed for your video hardware, as described at http://rpmfusion.org/Howto/nVidia. For example, I have a GeForce 6 and have akmod-nvidia-304xx installed. I think it's possible to install the wrong one by mistake, and don't know if one could have more than one installed at the same time.
If you have some packages from updates-testing and some not, then later disable updates-testing, your system can get in a state where dependencies don't resolve smoothly. This might be what's happening; editing your question to include the full yum command and output would help.