Ubuntu 18.04 black screen on reboot after upgrading to Linux Kernel 5.0?

My Lubuntu 18.04 (as a VirtualBox 6.0.10 virtual machine) is just upgraded to

Linux pbox 5.0.0-23-generic #24~18.04.1-Ubuntu SMP Mon Jul 29 16:12:28 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux 

with an apt upgrade. After the upgrade, the VM shows a black screen with a cursor in the upper left corner, and seems to hang.

Does anyone have similar experience with the new 5.0 Linux kernel, and know how to fix the problem?

FYI, I can go to the GUI anytime after hitting Ctrl+Alt+F1 and then Ctrl+Alt+F7 without a problem. A systemd-analyze blame didn’t show anything taking an excessive amount of time (3 seconds max) during reboot. But if I don’t switch manually, the black green never disappears.