All wireless N and still weak signal?

I have a wd tv live box that I have in another room from my computer running a home network. I have a cisco wireless N router and what I thought to believe a wireless N wd wifi connection. They may be 20 feet from one another so how do I have a weak signal??? I can stream netflix and pandora no problem but cant stream a 720p movie from my computer. I already checked the signal and I am dropping in and out of 2 bars so I know its not good right now. Whenever it drops to one bar the movie turns off.  Any Ideas on what to do in order to get a better signal???

What adapter do you have on your WD?

I have e exact problem on WD TV Live. Im only 12 feet away from my wireless N router.

The stream works perfectly well on my Android phone and Ipad at the same distance