Strokes in symbols not flattening properly with other background elements (CS5 & CS6)

Question

Hi There,
We have a bunch of round button symbols for navigational elements which are constructed in the following way:
Circle symbol with a fill and stroke
Circle symbol placed into button symbols (e.g. magnifying glass or arrow)
Button symbols placed onto page
This allows us to update the background circle symbol and have all the buttons (about 30 of them) update at once.
But when the symbols render on a dark background, they look like badly clear-cut raster images - i.e. the antialiased edges look like they've been flattened on white instead of merging with the background colour like a 24bit png.
Hopefully you can see the kind of bitsy edge in the image below to see what I mean:
I don't recall having this issue in the past - I've fiddled with the stroke settings but still no luck, here are the settings as they currently stand:
Is there a setting that controls this behavior that I might've changed or missed?
Cheers
Ben

Answer 1

There's a dirty little secret with 1-pixel strokes: They're not actually center-aligned. (How could they be and still stay sharp?) So your single-pixel stroke is actually aligned to the inside. And it's anti-aliased. What you're most likely noticing is the lightly-colored fill showing through the semi-transparent portions of the stroke.
A couple ideas on how to fix this: a) Set stroke width to 2px, center-aligned, and choose "Fill over stroke" under Stroke Options, b) Leave stroke width at 1px, align outside, and decrease the object dimensions by 1px, c) Set stroke to None and add the stroke using Photoshop Live Effects. Somehow, no matter which position is chosen for stroke alignment within Photoshop Live Effects, fill bleed-through along the outer edges is not a problem. However, every solution will change how the circle is rendered somewhat, so finding the best solution requires trial and error.