I have had a similar problem in the past. I was able to solve it and now my GC works well.
In order to get rid of the Handshake Failed, I did a complete uninstalled of the Google Maps and the GS software through add/remove programs. Then reinstall both using the GS CD. My test sequence is to connect to the internet, check in WKM Assistant to make sure that View and any other modules that you have purchased, Click and Go or Waypoints, are enabled. If not you need to get a new SN from your vendor. You will have to power up your WKM and connect it to assistant to see this info. After you have confirmed this, power down the WKM, disconnect from your PC, and stop Assistant. Then power up GS, making sure that you are using the latest version while still connected to the internet. GS will check for internet connection and once confirmed it should start to open. Eventually you will see a view of what I have been told is somewhere in China, if the clock is spinning let it go. It has take several minutes to start up initially for me. You can then plug in your GS transmitter. You should see an additional com port available to connect to. I have com 3 and 17, your system may vary. If you do not see the transmitter, check your ports in device manager and you should see the usb to serial com port. If not you will need to reinstall the driver. I have had this failure twice and after reinstalling, once several times, I have been able to make it work. I hope that this helps. I am using a HP NetBook running Windows XP Home Edition V 2002 SP 3.