Hi -
Usually I don't like to use dramatic words like "ruins" and "destroys," but basically that is what happened to two of my laptops after plugging in my 305 GPS on 2 MacBook Airs after installing the latest Garmin Communicator Plug In.
Steps to Repeat:
1) Macbook Air with Mavericks. Both laptops had this OS.
2) Test Page said I needed new GCP & 305 was not being recognized by test page.
3) I downloaded and installed Garmin Communicator PlugIn 4.2.0 with browsers closed.
4) On First Mac, I unplugged and replugged GPS. The computer shut down. Power button would not restart. Nothing I could do would start it, including tips from web forums. It is now scheduled at the Apple Store. Thankfully, I have Apple Care, but they cannot look at it until next week.
5) Not realizing that the Garmin caused the laptop to die, I waited until I got home to my other Laptop. This one also needed GCP 4.2.0, and I felt I was on my way to success until I plugged in the Garmin and the screen went black! This was all to familiar! Now I have two bricked MacBooks!
I feel that I can safely say that the problem is related to the Garmin. I'm not sure if it is the software - but it is worth noting that I had plugged the USB wire into my macs with GCP 4.1.0, and this did not happen. Also, I had been using the Garmin for many months with no such issue. It's hard to understand how the GPS could cause such a serious, fatal situation, but I assure you: it is repeatable. I suppose it could also be the device itself, or the included base. Note that on the second attempt, I tried a different USB wire.
Let this message serve as a warning to others with the same equipment mentioned above - as well as information to Garmin that other people may get their computers bricked: and possibly will become extremely angry customers. Computers aren't cheap, and neither are repairs (computer #2 does not have Apple Care)