Ok, so I realized myself what was going on with my image map. It was being auto-resized to fit within the specified CSS column. So I changed my image size a little smaller and it works fine now.
But, although on my mobile version of my site, using the WPTouch plugin, since it gets resized again there I was wondering what’s the best way to either detect which mode the sites in and substitute the image map with a mobile smaller version, or is there a way I can dynamically have the image, and coords re-align if it gets resized?