Hello.

Just wondering, 'ave you tried replacing the line

"connectAttr -f object_b object_a.rotateZ;"

with

"connectAttr -f $object_b $object_a.rotateZ;"

I reckon you're prob is a missing dollar sign (whatever the name for that is in the syntax).

I'm guessin they're variables you've defined in the mel code from the way you refference them. Since execution's making it past the other two refferences to them, I reckon that's your prob.

Simon