Texture alignment

http://imageshack.us/photo/my-images/4/textureissue.png/

So I'm trying to get this mechanic down but seem to be having a bunch of issues trying to get the texture to align correctly. I'm creating a quad with openGL calls and apply a texture to this piece of geometry. I plan on changing the texture on the fly and using it as the background but it seems to be off by a few pixels whenever I apply it to the geometry. I'm using a render texture from the camera to create the texture then attempting to apply it to the material but if I do this enough times you can see it starts dragging down. I thought it may be due to the texture not being a power of 2 but I tried changing the geometry to be square and the camera to have a square ratio but it still didn't seem to work. Is this an issue with texels? Any help would be greatly appreciated, thanks!

Also if someone knows a better technique to save what a camera sees and apply it to a texture would be awesome.