My experience with a new LG 5K ultrafine monitor reminded me that modern personal computer systems are collections of computers.
I have one of the new 13" Macbook Pros with four USB C ports. I also have one of the new LG Ultrafine 5K monitors to use with it. Ever since I got the monitor, I've had all kinds of problems. The display will work for 10 minutes and then start resetting (acting like no display is connected, then reconnecting, then repeating) until the laptop gives up, freezes, and eventually restarts. I was hopeful the latest MacOS release might fix it, but it just kept on acting up, even after installing the latest.
I was about to give up on the monitor and just go back to my old reliable 27" Thunderbolt display. I tried disconnecting everything, rebooting the computer, using different ports...basically everything I could think of. Then I remembered one computer I hadn't rebooted: the monitor. Sure enough, unplugging the monitor from power so it was forced to reboot solved the problem.
My theory is that the monitor had gotten itself into a weird state that merely disconnecting it from the computer couldn't reset. The monitor is one of the computers in a distributed system. There are others, of course. We're already used to things like printers being computers in their own right because they have a network connection. But the monitor, keyboard, mouse, and even cables all have computers in them that have to cooperate to provide the personal computing experience.
So, next time you're computer isn't working, you might just need to reboot one of the cables.
As an aside, the LG 5K Ultrafine is an incredible monitor: bright and clear. But it's not much of a hub because it has three spare USB C ports so you still have to have all kinds of dongles. What's more, the 13" Macbook Pro can only drive one of them. And even with a 15" Macbook Pro you can't daisy chain the monitors—not enough bandwidth.