No shadows with splitscreen

I'm currently working on a project involving a head mounted display which uses the side-by-side method for creating the stereoscopic effect. To achieve this I use splitscreen with two cameras, but shadows only shows up in the editor, not on play or build! However, if I only use one camera, it works just fine. So why won't unity render shadows when using two cameras? I've tried with both directional lights and point light and of cause remembered to assign hard shadows.

I'm using unity 3.5.5f3

Please help!