Black splodges on ceiling

[Imgur Album][1]

I have these black splodges in the connection of ceiling and wall. Light resolution on ceiling and wall is 512. One UV is included in the album. Any help is really appreciated.

Hi!

Your lightmap resolution is for sure low! …where you have the lamp you can see the pixelated shadows on the wall…
A question: are your walls planes or meshes with thickness? Also: are they edge snapped /walls with ceiling or each other) or overlapping where they meet?