If you started writing scripts with mzscript in 0.9.13, you can't switch halfway through to 1.0-rc2, and vice versa. Atleast not without some changes to what you've already written. Not saying you did that, just mentioning it, because some of their syntax isn't compatible. That would explain why you're getting errors with one version and not the other. You have to pick one to stick with. Either versions are good. I personally prefer 1.0-rc2, though, but you can't have ;comments in your vars file if you use it.