Rat a Tat noises coming from my bottom bracket area. Please help!
I think it's the single speed freewheel.

I've just been through almost exactly the same thing with a brand new Cross Check SS. From day one I had a fast, regular clicking when pedalling, about 4-5 noises per pedal revolution. I could sometimes get it to calm down by pedalling backwards a bit. I was convinced it was the bottom bracket too, until I got the whole crank section rebuilt and it didn't help.

Eventually found some forum posts that described a problem with some SS freewheels, e.g.:


http://www.bikeforums.net/singlespeed-fixed-gear/436916-freewheel-noise-while-pedaling.html
http://forums.roadbikereview.com/general-cycling-discussion/whats-knocking-my-single-speed-211923.html


My bike came with a 17 tooth Shimano freewheel. I got a White Industries freewheel instead and it's been a dream (although the normal ratchet noise when freewheeling is louder now).

Could you try a fixed cog or another rear wheel to eliminate the freewheel?