Hi,

I recently ran "guix pull" and then "guix system reconfigure" on a
GuixSD installation in a VirtualBox VM.  Since doing that, I can't log
in.  While booting, everything proceeds as usual, with normal output,
until the SLiM login screen is supposed to appear.  But instead of the
SLiM login screen, I get a blank screen with a small white cursor in the
upper left, and I can't log in.

Has anyone seen anything like this in the past?  Here are some
observations I've made about the situation:

* GuixSD shuts down normally if I issue the "shutdown signal" from
  VirtualBox.  This indicates the OS is actually still running.

* I waited over 8 hours, and the login screen did not appear.

* I tried blind-typing my user name and password, but the blank screen
  remained.

* When I boot from the previous system generation, there is no problem.

* When I replace SLiM with SDDM in my OS configuration and reconfigure,
  the same problem occurs.

* However, one time only, while trying to boot using SDDM instead of
  SLiM, I got to the SDDM login screen.  But when I typed in my username
  and password and hit enter, I received the same blank screen as before
  and ultimately could not log in.  Every other time I've booted the VM,
  I didn't even get to the SDDM login screen, so I don't know why I was
  able to reach the login screen that one time.

* I tried pressing control+alt+F2 etc. to switch to different virtual
  tty, but it didn't work.  The blank screen remained.

* I examined various system logs, but I could not find anything that
  jumped out at me as causing the problem.  It's entirely possible I
  missed something important, though; I just checked a few places.

There is more that I could try - for example, I could try starting an
ssh server in my VM and logging in that way.  I could also try drilling
deeper into the X server logs, since that seems like the obvious next
step, since the problem occurs for both SDDM and SLiM.  I could also try
reinstalling GuixSD in a new VM.  But I haven't tried any of this yet
due to lack of time.

If anyone has any advice or has seen this before, please let me know.
Thank you!

-- 
Chris