So I unloaded the Prolific driver I was using that was from some open source
project, and loaded the one downloaded from the Prolific website you pointed me
at, which at least claims to know about OS X 10.7, and I expect it likely is a
better choice all around.

Dan,

Actually the behavior you are describing seems to be pretty common. I've fought with the same thing for a while myself. The thread he was pointing to was one just from a week or two ago. In the end, this driver works (actually, worked, haven't tried since upgrading to 10.8.x yet) for me on 10.7 at least.

http://xbsd.nl/2011/07/pl2303-serial-usb-on-osx-lion.html

I will do my best to test it on 10.8.2 sometime today or tomorrow as I need to fix my wife's VX-7R with correct power levels since they are totally messed up from a bug. The source code is available so if it doesn't work, I'll look at recompiling with 10.8 and the latest XCode and see if that works... if that doesn't work... I'll see if I can figure out how to port it.

Hopefully it just works. If you download it and it works for you on 10.8, that'd be great.

BTW, the problem is that the official Prolific driver on MacOSX has some counterfit chip detection built in... or at least the counterfit chips aren't as tight with timing or something and the official driver stresses them and thus the failures. No matter what, the official driver unless you have an official chip on MacOSX is an iffy proposition.

Jay, WC3K