Baked light map for level appears to be dirty

I am baking light maps for a level. However, after multiple bakes I find myself getting “dirty” light maps. The material on most of the surface is simply a grid (textured 256x256) I made in photoshop. When I play the game, there seem to be random smudges of colors everywhere on the maps!

[24595-screen+shot+2014-04-01+at+6.16.36+pm.png|24595]

I have the following options set up in unity. What’s causing these aberrations? In a scene like this, what is the optimal settings? This bake is almost 100mb but the quality isn’t as I hoped…

[24596-screen+shot+2014-04-01+at+6.17.43+pm.png|24596]

It seems to have something to do with “compressed” option in the Maps tab. I ticked it and unticked it and everything is good.