I've just set my SS up as a fixie. No problems the first week or so. I now get some "cluncks & twangs" from the rear end (as far as I can tell as I can't seem to recreate it on the stand). The bikes rear end, BTW.
At first I thought the chain may have a tight link, but don't see one at least under no-load on the stand. I've been playing around with my chain line to see if that helps. Looks like I have to snug up my cones a bit because there's a little too much lateral play, Anything else I might be overlooking? I'm probably due for a b/b re-build too, but I don't think that's the issue.