As mentioned in this FAQ mk2 players with serial numbers less than about 1050 have ground missing on the serial connector. It is necessary to ground your laptop's serial shell (or other attached stuff) to car ground with a separate wire. I can understand that in some cases this extra wire looks very unprofessional or is difficult to implement in the car. When I was stumbling to get the connection working last week (I knew about the problem) I found out that my car cigarette lighter adapter for my laptop solves this problem also! So there's no need for an extra cable. I think it's a nice solution, looks rather professional also and additionally keeps your laptop's battery from drowning. I use an universal adapter. You can set the voltage and polarity with dip switches. It's rated for 15-24V 3.2A (or 60W max). Several different tips are included for various connections. And it isn't expensive.

Edwin de Vaan
mk2 rev.7 Trillian # 080000263 6Gb blue/red