malakim, have you tried assigning a static IP address to the NAS, or at least increasing the length of the lease for the IP address? If increasing the for the IP address reduces or eliminates the problem, then we would have verification.
No, I haven't tried that. The "router" I use normally is a crappy modem / router delivered by my ISP that doesn't allow any configuration. However, I also have a NetGear wireless router that I use as an access point. I could try disconnection it from the Internet and just connect the SB and NAS to it and see if that works better.
I'll try it during the weekend and post my results here, OK?