Graphical login hanging after password entry

[carlosqueso]

I'm using the stock Manjaro install.  I got things set up fairly well about a month ago, but haven't had time to get it out for a few weeks.  A day or two ago I powered it on, and entered my password at the graphical login screen as usual.  When I hit Enter or click the Login button, it turns solid green and then freezes that way.  The mouse pointer still moves around in response to the trackpad, but everything on the screen is unresponsive from that point on.  Fortunately, I can restart it with Ctl-Alt-Backspace.

Login on the alternate consoles is unaffected.  The only process running on tty1 is Xorg.

I discovered that after enough attempts, and maybe changing the session manager from the list in the lower left corner, I can finally succeed in logging in.  Sometimes it's after a dozen tries, though.

I had not changed any packages since the last time it worked normally.  I rebooted several times, but no change.  I applied all the software updates (200+) and rebooted.  Still does the same thing.

Does anybody have any clues what might be going on, or how to debug further?

TIA for any suggestions.

Are you using mesa-git by any chance?  The last two versions of it caused kwin to hang (I managed to get in the second time, but maybe yours doesn't).  If that's the case, it's an easy fix.  Just follow the instructions in this thread: https://forum.pine64.org/showthread.php?tid=11598