F15 Alpha will not start after my last yum update

[Petrus de Calguarium]

Also, so that you can see that something is happening during those up to 30 
minutes, type ESC once to switch plymouth graphical boot to show the boot 
output. Things will be very slow, but mine did eventually get to a graphical 
system (I also had to hit alt-SysRq-r or even alt-SysRq-re, I think, to jog 
things in order to get X to run).