KAWAMALL cable did the same thing. Guess MacOSX (or at least mine) and Prolific and Yaesu Uploading of programming just does NOT work. Bummer.
Well, the (prolific adapters) will work, there are many people on the list that use then (and it shouldn't be related to the VX-7). However, it sounds like there's a potential driver issue that needs to get worked out. If you're interested, Debbie Filgor on the users list is a very competent Mac power user which I'm sure could help you.
That said, picked up a Tripp Keyspan USB-Seria. Worked awesomely well, so now have my VX-7R (that my wife has taken over after getting her ticket a couple of weeks ago) working just fine.
Excellent. Keyspan devices are, without a doubt, the highest quality USB adapters I've found.