Unfortunately, "it works for me" isn't actually that useful a data point 
It's not a software issue as I haven't changed any resident applications on my machine between previously using an Atheros card with no issue, and now using the Intel card. No BIOS-level power saving settings. I've tried setting the Windows power savings options to not allow the system to put the card to sleep, that made no difference.
Anyone from Intel have additional troubleshooting steps I can take, or maybe information on setting up some kind of debug or verbose output from the driver to see what state the device is in when it stops passing traffic?