Image resolution bug in WordPress 3.5

Hi, I upgraded a couple of sites to WordPress 3.5 yesterday, but noticed that it made some of the images drop in resolution, for no apparent reason.

I’ve tried re-uploading the images, but it made no difference. Examples of what I’m talking about are here:

– The banner on http://www.createasustainablehome.com.au (you can even see over on the left hand side, there’s stray black pixels, which aren’t in the original image, and definitely weren’t there before the upgrade).

– Also, the 3 feature boxes at the bottom of http://www.ladybirdcarpetcare.com.au (for example, the ladybird should look like the one at the top of the site, but it doesn’t now).

So weird. Any help would be greatly appreciated. I’m regretting upgrading to 3.5 at this stage.

Thanks