I have a MS Server 2008 domain setup. IT appears that around 5:30 - 6pm the users loose connectivity to the server. If they are logged in to an application hosted on the server they loose connection to that app and everything else.
If they log off and back on all is okay.
I am not onsite, I am a consultant for this company. I have also noticed that if I try to RDP to one of their desktops after hours I can not connect, but can during the day.
I did see where the NIC was being controlled by the OS so maybe that was it, not sure yet just did it.