Panasonic HS400 freaks out when switched to HD settings

I'm co-director for a video team for a small church. We currently run two Canon XHG1s connected to a Panasonic HS-400 to live-capture Sunday sermons and events. The problem is this: the signal on the cameras is set to 1080i (60i), but when I change the system setting on the HS-400 to 1080i (59.94), the multi screen display flickers out, returns with green static running across the entire multiscreen layout, then flickers out again and when it comes back the inputs are black.

We had some help setting the system up for standard def, but we want to make the transition to HD and we can't figure out why the system goes green then returns to normal, let alone why it won't accept the HD signal.

We're still learning how to use this setup so any pointers are appreciated.

Thank you,
Dan