Front page banner image – display issue on iPhone

Hi there,
I have installed this theme on my site and it’s really cool – thanks!!
The only problem I have come accross is the display of the front page banner image on an iphone.
It appears perfectly on every other browser that I have tried (even safari on windows) but on the iphone (safari of course) the image is only about a third of its normal width…
Any ideas how I can correct this in the code? This is important to me as I will be offering mp3 downloads to mobile phones so I really need the iphone display to work correctly.
My site is liamgall.com.
Here’s a link to how the front page looks on my iphone: http://www.liamgall.com/images/banner_issue.png

Thanks in advance!