Error using BarsOfData  [SOLVED]

I'm trying to make an indicator which references multiple instruments.

So far, the code is really simple.

protected override void CalcBar(){
// indicator logic
var i1 = BarsOfData(1);
var i2 = BarsOfData(2);

var ins1Val = i1.Close[0];
var ins2Val = i2.Close[0];
}

The line "var i2 = BarsOfData(2)" gives me an "Error in application" exception.
Attached is a screenshot of the instruments I'm using.

What am I doing wrong here?

I found the answer to this here:
viewtopic.php?f=19&p=97924#p97924