Same as you, I can see the files on my windows 7 system and I use a USB memory stick with no external power.
Problem is not with the PC but with the TV and Bluray player not fully recognizing the media server. I sent you screenshot in my email.
Anyway, tks for all your time and efforts. I will probably ended up picking a Belkin N600 or N750.
It is cheaper than the 645 , has a working media server and Dual Band.