Yeah.. looks like your shadow and highlight layers are still rotated, mate.
If you really need to look at your 'canvas' from another angle, the best thing would be to rotate the whole thing:
Image>Rotate Canvas>90deg CW - then do your stuff - then rotate it back:
Image>Rotate Canvas>90deg CCW.
Best to stick to 90deg and 180deg rotations... or the image quality will become distorted.
