3d object rendering as red / green blocky mesh

[Bill35972152zj1z]

I had imported a mobile phone 3d model and all was working well.  Then, after displaying correctly for a few seconds, it suddenly appeared like this.  For a while it was rendering correctly, then startedflickering.  I started playing around with keyframes and rotation, and now it suddenly won't render correctly at all.  Any idea what's causing this?