F22 unusable - system freezes on login

[Matthew Woehlke]

(First try apparently got eaten; apologies if this is a duplicate.)

I just installed F22 (KDE spin) from scratch on a new Dell M6800. The
Live CD seemed to run okay, but when I try to boot the installed OS, it
(almost¹) invariably freezes when I try to log in. The machine is
effectively unusable as a result.

Has anyone else encountered this? Can anyone recommend a course of
diagnostics? I'm unable to even get the machine into a state that would
allow remote login (over ssh anyway, and I don't know offhand how to set
up serial login), and I've not seen anything in /var/log/messages that
might indicate a problem.

(¹ *Once and only once* I was able to log in, but the system froze as
soon as I tried to run an application. Also, I can log in in single-user
mode, but this isn't good for much but running dnf and fiddling with
enabled services. I *have* applied all updates as of a few hours ago to
no effect.)

-- 
Matthew