first post here, and this has probably been covered somewhere before, but I thought it might be helpful for me to post a little solution I found when my console *suddenly* stopped detecting PS3MS after a pc/router restart.
Anyway, I went through the faq when I had issues, and found nothing I tried from there worked (there might be more posts there, but I'll be first to admit that I didn't dig TOO much - google was pretty useless in this instance).
Now I would get this in the Traces (everything before this message was fine):
INFO 2012-05-02 19:32:23.156 [main] The server should now appear on your renderer
INFO 2012-05-02 19:32:33.862 [UPNPHelper] No IP filter specified, access granted to /10.0.0.4
after that last one, it just wouldn't detect my console.
BUT that ip you see there, kept sticking to 10.0.0.6, which was another network card in my pc,as opposed to 10.0.0.4, which I wanted to use. Forcing the networking interface under General Configuration wasn't working either.
So I went to Network and Sharing Center -> Change Adapter Settings then disabled the other network cards. closed PS3MS and restarted it, turned console on - and lo and behold, it detects PS3MS without a problem.
Turns out that the network cards were conflicting with PS3MS, and the force networking interface setting wasn't changing that.
Hope this works for others who might have a problem too, just another idea to try for those with multiple network cards/interfaces to try. Pretty obvious really, but sometimes the obvious solutions avoid you!