Hello @aristath, i have the same problem (without the cloudflare)…
i tested with 1.6.2, 1.6.3, 1.6.4 & developer version
i think the problem is only if someone theme have customize image sizes add on functions.php theme. if they don’t use or just use the 3 native sizes on wp media section we don’t get any http error. i think the problem is just the customize image sizes
@b_dark so if for example you use the plugin with the twentytwelve theme that doesn’t use any custom image sizes you don’t get these errors but you get them if your theme specifies image sizes other than the default ones?
@nickth could you please try using the twentytwelve theme so that we may verify that it is indeed an image_size issue?