USB ports dropping like flies

Hello,

I've begun having a problem with my USB ports delivering power to inserted flash drives, but not reading them - Windows Explorer shows nothing in the drives and the "safely eject hardware" option isn't available.

The problem started with one "fussy" port a couple of weeks ago, then over the past weekend, I was unable to get any of the three available ports to boot a flash drive. I tried different flash drives which all work on other computers.

The fourth USB port runs my mouse without issue.

I have run virus/malware scans with no results. The computer (HP Envy running OEM Win 8.1) is working fine otherwise.

UPDATE:
After multiple reboots, system updates, & uninstalling the USB ports thru Device Manager, I have partial ability to use the ports. Not all of them are working, and every time I get a flash drive to read, I get the "device is busy & can't be stopped" message when I try to eject. (When this happens, I eject by shutting down the laptop, removing the flash drive, and then rebooting the laptop.) This problem has been going on A LONG TIME, and may perhaps be directly related to the ports not being read.