I think you might have got double folder syndrome. If you're downloading to your CustomTextures folder and unzipping them there, then Windows always makes another folder to put them in. As the textures are already in a folder you end up with two of them. Have a look at the folders in question and see if there's a folder in a folder. If so take the second folder (with the texures in) out of the first folder and place it directly in the CustomTextures folder. What you should have is one folder named 'texturename' and inside that the textures themselves.
The way to avoid it in future is to unzip the folders as you are downloading them by choosing 'open' instead of 'save' in the download box. Then when it's opened it, choosing 'extract all files', then browsing to your CustomTextures folder and extracting to there. This way it doesn't make another folder and you will get just the one folder with the textures in, and everything should work properly.
Hope you can follow that.
