I was using my Ubuntu 22.04 desktop when all of a sudden everything froze except the mouse pointer. Switching to a virtual terminal with Ctrl+Alt+F3 worked fine. When I rebooted, it allowed me to log in normally, but then when I reached the desktop again it was again frozen apart from the mouse - nothing would respond to mouseovers, clicks, or key presses, not even the shutdown menu (except that Ctrl+Alt+F3 still worked fine, as did Ctrl+Alt+F1 for an alternate GUI login page, which was not useful because if I logged in it had the same problem).
I don't know what might have caused this. At the time I was using a VirtualBox VM and hadn't opened or changed anything recently.
Guessing there might be something wrong with the desktop packages, I tried:
apt-get updateapt-get dist-upgradeapt-get autoremoveapt-get autocleanapt-get install --fix-broken ubuntu-desktopwhich all succeeded without any errors, but did not help with the problem.
On the login screen, using the gear button at the bottom right, I was able to switch from "ubuntu" to "gnome classic" and log in, and now it is not frozen!
However, "gnome classic" is not my preferred interface. I would still like to understand how to fix the problem.
When I reboot, switch back to "ubuntu," and log in, it is again frozen. I tried journalctl /usr/bin/gnome-shell and saw the following errors: https://pastebin.com/wyNSNr4W the ones saying "unable to update icon for multiload" look like they could be relevant. I do not get these errors when I switch to "gnome classic."
What could cause a completely frozen desktop?