The Dell Latitude E6400/E6500 and other computers based on the Intel Gigabit 82567LM network card will drop offline during power save modes (including when Windows is set to “Turn off the display”).  It’s an Intel Network Interface technology called SIPS, System Idle Power Saver.  It’s highly frustrating, especially because mapped drives may not reconnect upon restoration from the display blanking power saving mode.  I’m running this on the Nvidia version of the Latitude motherboard under Windows 7, but I’m guessing this same issue may apply to other versions of Windows including XP and Vista.

In certain versions of the driver, the settings are only exposed via the registry in a cryptic area.  Here’s the post I used to fix the issue on my machine:

http://communities.intel.com/message/86578;jsessionid=1F068452291822CA757E55B5FEB8F5E5.node6COM#86530

Since the registry edit is fairly advanced/cryptic, HP has released a utility to do the modification automatically.  Apparently this utility works perfectly on all brands of desktop/laptop.

http://h20000.www2.hp.com/bizsupport/TechSupport/SoftwareDescription.jsp?lang=en&cc=nl&prodTypeId=12454&prodSeriesId=3785404&prodNameId=3785039&swEnvOID=2097&swLang=13&mode=2&taskId=135&swItem=vc-80464-1

This took quite a bit of digging to find, so I’m archiving it here along with some keywords (specifically Latitude E6400/E6500) that might make life easier for others Googling for the same solution.