Hi,
I had the same issue with the PinBlack theme and these 2 changes seemed to fix it (at least on the iPhone simulator):
styles.css: remove “and (min-width:321px)” in the first media query rule (around line 1066 in the css file)
header.php: modify the viewport meta tag (line 5) to “<meta name=”viewport” content=”width=device-width, initial-scale=1.0, maximum-scale=1.0″ />”
I’m not sure if the latter mod is needed, but I believe it’s the common setting for mobile.
Hope that works for you – I am fairly new to WordPress. Current site is here