I was just doing a couple quick renderings with both RPC's and decals. I was using the default sky and rendering engine 1. I am getting hazing at the transparent areas of both again. This issue occured several months ago with engine 0 and was corrected there.
I am using windows 7, architecture 2011, and build 255 - all 64 bit.
I was about to download build 256, I don't suppose that your bug fix will also take care of this but I'm hoping.