I am displaying different content depending on how the user is holding his/her phone using the onorientationchange call in the body tag. This works great - I hide one div while
I had this issue too I think.
Try putting a "maximum-scale=1.0" (and maybe a "minumum-scale=1.0" if you feel like it) in your viewport tag.
This assumes you don't want the user to be able scale though (which I don't)