Problem in alpha channel in Vray for Sketchup

Hi there, in a senseless reset of my Vray settings, I have stopped seeing the background in the alpha channel, that is, now I have a floor and my object is above the floor and the background is the default Sketchup, but when I render, the background comes out as a smudge, and not invisible, and when I enter the alpha channel, the white background comes out, just like the object. So when I save the png it does have a background and my object is not floting as I wished, any ideas?