ARTYSTA, FERRUS126: if you have any issues specifically with AO and you're sure you have proper lightmapping UVs (please check the case http://issuetracker.unity3d.com/issues/gi-global-illumination-baked-intensity-slash-direction-uv-maps-overlapping-causing-blotches for details) then please submit bug reports that show them. It's unlikely that this case is related to your issues.

The issue is fixed in 5.2.

My issues went away when I discovered that the Max Distance was a value from 0-1 (based in Units) So if you wanted the AO to effect the entire unit, that would be 1. Since moving my Distance to 0.3-0.5, I can see the AO the way I want it and all of my Black Spots issues went away.
An AO of 4 and Distance of 0.5 looks great (for me and my game)

After extensive trail and error I have come to the conclusion that when the Ambient Occlusion setting is greater then 0, the farther the target mesh is from the center of the scene 0,0,0 ( I put it at 2000,0,0) the worse the artifacting (black dots and distortion) of the AO in the lightmap gets. If the mesh is at 0,0,0 the lightmap renders fine.

Having the same issue here. Tried a variety of different light map settings with no luck. Increasing the resolution does decrease the size of the black dots (they become fine points) but does not reduce the amount of them or solve the problem. I have a relatively simple mesh with simple UV's. I do notice a concentration of the black spots around the triangulated vertices.

Same problem here. I find enlighten stunningly buggy, incomplete, slow, with inadequate documentation or controls to better optimize performance.

Some meshes bake fine, others show this artifact. Haven't narrowed down though exactly what about the mesh throws off the baking process.

Same here, have to manually fix them in PhotoShop for final build.

I am having the same issue. This was a problem in Beta but it seems to have came back. I have scenes that have been fixed. After I updated to 5.0.1, I ruin my scene. I cannot get proper bakes now. If I up the rez on that mesh, the problem seems to move on to another part of the scene.