Thanks Jim ... I was noticing the same problem during my testing.
This thread is a real life saver to discover so quickly. Thank god for search on these forums.
Just got my first Lynx Express and DMX Dongle done and everything works, but this green light going out (after a while) ... really had me concerned about future stability issues using the Lynx DMX Dongle.
I am using Windows 7 64 bit ... here is what I did, since I wasn't sure how to get into the USB settings you mentioned:
Click on windows7 logo ... typed into search box "power" (no quotes)
Click on "Change power-saving settings"
Click on "Change Plan Settings" (this was next to Balanced settings, which was already selected)
Click on "Change advanced power settings"
Scroll down to "USB settings", click the "plus sign" to open it up, if necessary
Click on "USB selective suspend setting"
Click on "Enabled" will give you a drop down list box, choose "Disabled" instead.
Click on "Apply", then "Ok"
This procedure might need to be listed someone either a sticky or in the wiki ... because I bet a lot of people have had this happen, since this is a windows 7 default.