I am no expert but maybe that's a good thing cause I wont confuse you with technical speak.
I have had my share of problems with a microRendu based system and I can say that every time it was not the microRendus fault.
I also have a NAS and router (cisco 8 port terminal) set up and had to wrestle with different settings in those systems.
One little thing that took me a while to figure out was that my DAC was cycling on and off without me knowing and that would cause connection problems with the micrRendu.
The Sonore guys are awesome and worth contacting, but beware, its not fair to expect them to solve all the problems in your network.
Whats your NAS and Router?