My problem occurred a couple days ago.
My first thought was that the TV might have updated it's firmware without your knowing it and caused the problem. However, the other things you report here make me wonder.
I have refreshed the UPnP AV server many times but to no avail.
I cannot even access it on my macbook through finder. I get " Can't be opened, because the original item can't be found"
Well, the obvious question would be have you tried restarting the NAS?
The error from the macbook smells like a link that you were using to access a network share which is no longer available.
I would check to see if the NAS is advertising the shares. Use CMD-K to bring up the mount option and hit browse to see what it tells you.
You "should" see your NAS on the network and the shares it is making available.