I've been following this thread, even though I'm running an Intel P4EE CPU.
I have a gut *feeling* that we're suffering from a similar problem, but, in my case, it doesn't stop me from booting.
Since I installed the 3.7-rcs, I cannot get my drives to mount in "recovery mode". When I try to go into read/write mode, I get an error dialog saying it cannot mount "/" because it doesn't exist, and so forth, and so on. However, it will boot, during a normal startup.
As a workaround, I've been going to console from the LightDM login screen, and disabling services, instead of using "recovery mode".
Reading thorough this thread, it sounds like you guys aren't getting that far in the boot process -- that's all.
The 3.7-rcs obviously suffer from a litany of issues. Hopefully, we'll overcome them soon.