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.