You could try this.loadMovie("image1.jpg");

I think it could be scope issue. From what I read it goes as follow:

images>image_1>loader_mc1<AS code on this MC

I think your current code is looking for loader_mc1>loader_mc1 (movieclip)
Or, if the above works, then just put the code outside of loader_mc1, like so:

images>image_1<put original AS code here

Hope that makes sense and works