OS X 10.10 Yosemite both systems. The USB stick is HP (Hewlett-Packard) x900w so it's not trash.

I have an external USB stick that was malfunctioning on another system. I brought it to my own system, and it's causing a weird problem.

Every app which tries to interact with it, the app freezes indefinitely. It's done it on both systems. It'll work for a short while, and then POOF. There's no recovering; hitting ctrl-C on a Terminal app (e.g. running ‘du') hangs up the shell – ctrl-C does nothing. Word and Excel are not interacting with that drive, but still hang hard. Finder and Disk Utility lock up when asked to interact.

Physically yanking the USB drive unlocks all apps and the system returns to normal.

I was finally able to dismount and partition/format the disk, but now ‘cp HugeVideo.mp4 /Volumes/Untitled/' causes it to copy properly for about a second, then do nothing for 30 seconds, then burst copying for another second, and the copy never finishes and nothing works.

Is this just a plain old failure of the USB drive?

But the crux of my question: if a USB drive is having read/write errors, why does that indefinitely lockup every app?