The scene is on Bespin, right after the new Cloud Car flyby (after they've been there awhile), the scene cuts to Leia pacing in that lounge (Han walks in, she's worried about 3PO, etc.)
In the original version, the ceiling in that room had open slats and extended upwards to another set of slats where a sky light would be (you didn't see the actual sky light window, but saw light coming through with slats casting shadows that suggested a sky light.)
In the SE version, they filled in the lower slats with blue, giving the very poor impression of a skylight (I think they might even show a cloud car fly by over it.) What they didn't fix were the shadows that the slats higher up were casting. Now we've got poor looking windows (the edges are all fuzzy) and shadows that shouldn't even be there.
What's more, they didn't even need to do it! Though the exterior shot of the building in the SE is different than the original, the top of the building isn't that much lower that they needed to make the sky light visible in the interior shot. The camera angle isn't that low, so it's still completely plausible that there's a skylight in the ceiling just out of view.
The lighting looks so unnatural with the bad cgi skylight in that scene, it bugs the heck out of me. If it's possible to just restore the pre-SE scene, I could stop cringing when I watch that part.