kextstat reports this is the Prolific PL-2303 driver, version 1.5.1. -- com.prolific.driver.PL2303 (1.5.1) <81 38 5 4 3>

I don't know if this is a counterfeit part or not. It's an actual Baofeng cable, but of course that doesn't mean it's an authentic Prolific part.

OSX version is 10.10.2.

Chirp is programming the radio, in case I wasn't clear on that. The lock-up will occur unplugging the radio, unplugging the cable, and usually when closing the program, regardless if the radio is powered on or not. I've not been able to make the hang occur when closing the program and I HAVEN'T opened a connection to the radio.

What happens when you open/close/read/write/unplug the serial port using another serial application? Here's some instruction for doing this with screen: http://pbxbook.com/other/mac-tty.html

The reason I ask is that there are three things that can cause a complete lockup:

OS bug¶

driver bug¶

hardware issue, such as power supply or memory failure¶

Chirp, as application software, does not have the permissions required to take over your system like that. My money is on the lockup being caused by your USB serial driver.