I have 2 os-x machines running prince, one is my development laptop and another is a mac mini that hosts our internal site. Everything works correctly on my laptop, but I get the following error when I run it on the mini through my rails application

undefined method `size' for nil:NilClass

So I know the code works fine. Thought it might be fonts as with most linux setups, so I copied all the fonts across but no luck. Does Prince require xcode tools or anything else like that?

That looks like a Rails error, and is unrelated to Prince.