I have a Samsung BDP (not your model though) and have no disconnect problems. I have a similar setup to you - except I use Mezzmo instead of Servio. You could try the free trial of Mezzmo and see if does the same to help isolate the problem. If it does the same, then I agree - your D5100 BDP seems to the problem. Another thing to try - check if your router has UPnP turned on in its settings. Turning UPnP off in your router often helps with DLNA streaming. Reboot your router after making any changes.