I have been using static ip addresses for my Media Server and also for the MediaLounge ever sense i set everything up. The IPs aren't manually set on the server but are set through my router (IP associated with the mac).
i too have a wii, an xbox, and a few laptops that don't have any issues with the wireless (wii and xbox also set with ip/mac relationship in router). I don't have any wireless phones (we use cells only). I also tested media lounge with everything shutdown except for the media lounge (server is hardwired).
when reading some of the firmware release notes i noticed that in 1.06 there is a viiv network time-out of 60 minutes added for configuration.
"¤ Changed Intel Viiv wireless configuration time-out period to 60 minutes."
it says it is for the configuration but this makes me think that there could be some time-out period set or this variable is crossing over to the main program.
maybe there is a wake up problem coming out of the screen saver or returning from a stream. a simple refresh seems to cure the issue, maybe a "refresh" could be added after a screen saver call or when a job is cancelled/completed (i.e. streaming, photo load, music playback, etc.)
Maybe this is a Nero 7 quirk? When you do your tests are you using WMP11 or Nero 7?