Last modified: 2014-02-12 23:45:41 UTC
This is because innerHeight lies on WP7 - we need to add height=device-height to the meta viewport tag (we should be cautious in case this has unfortunate side effects..) http://jonrobson.me.uk/mobile/innerHeight.html
I tried to add an IE specific hack in the css using a media query for landscape only and realised that the phone I'm testing on still thinks its in portrait mode when in landscape. It's a bug in Windows Phone 7 and I don't think there is much value in working around it.
Easiest fix would be to turn off the references enhancements for this browser but since this does work in portrait mode and thus it can be worked around I think this should be ignored as this is a browser bug.