Weird white borders?

Alright, so I'm currently working on a Saira LP, and I figured that, to show off everything, I'd show off the editor at the end, and to do so, I've been working on creating a sort of "Night Time Lomond."  However, I've found that, after darkening the "Ruins 1" object, this weird white border now forms around it if it takes on a rotation other than 0/90/180/270 degrees (see attached file).  What can I do about this?

My guess is there's something wrong with the semi-transparent parts of your Ruins 1 image. I'll need you to attach that image, so we can inspect it.

Alright, here it is. 

The image is the problem. Graphically it's fine, but the format is incorrect. When you export to a .png file you are saving the colors for fully transparent pixels. Then, when you rotate the image in the Saria editor these invisible colors are blending into the visible pixels.

To prevent this issue in the future find your photo editor's setting for saving transparent pixel colors and turn it off. In GIMP these setting appear as you export a file. I've attached an image of my default settings for .png files. I turn off everything and set compression to max. (Compression affects opening time and file size but not quality.) Note: I use an older version of GIMP because I don't like the newer versions.

Ah, it worked!  Problem solved! Thanks a bunch, Egomassive.