I dont have your set-up, but I doubt its anything to do with the router as both the TV and PC are on the LAN side.
Just a thought... because Im clutching at straws... but could it be an issue with Windows7 sharing. I know that Windows 7/8 can be a bit of a bugger sometimes for other operating systems to see. I have music on my d-drive that should be available to share across my network, but an old XP machine used to have a devil of a time trying to see anything on the Win7 machine. Sometimes it worked, sometimes it didnt. The Win7 machine could see the XP machine absolutely fine. I never spent much time looking into it though because the XP machine went to a new home soon after... TBH I used to cheat by using the Win7 machine to dump files, rather than pull them down directly at the XP machine.