Welcome to the forums! Just a couple of questions:
So, the tracks you acquired from the DG-200 is showing the local time correctly?
When you mean 'plot a track directly on Google Maps', are you referring to the Google Maps of the DataCenter program (the software that came with the device)?
It was also showing the time correctly in Google Maps, right?
Perhaps, the program lies with the Adobe PS Lightroom 4. To confirm if this is the case, you can try checking the gpx file with Notepad and review the time.
Moreover, you can possibly try Locr program and see if you're able to see that issue. You can find more information about the program here: http://www.locr.com/learn-more,2
Also, can you please register your product and generate a support ticket? Please check your email for further instructions.