Fonts not appearing correctly after importing book to different computer

I was working on several books on a Mac mini running Leopard, but recently switched to a Dual GHz PowerPC G5, also running Leopard. I exported my books on the old machine and imported them to the new machine. However, the three fonts I used most frequently—Scala, Futura, and Garamond—all look different on the new machine; both the faces and the sizes are different, causing the text to re-flow in a very disruptive way. I’ve tried re- importing the fonts to the new machine and while they now look similar, they’re not identical.

I wrote to Blurb tech support but they claim it’s a Leopard issue… and the Apple discussion boards are full of people having font problems in Leopard. But it just seems to me that if I created a book on a Leopard machine and then exported it to another Leopard machine, it should look the same on both machines. Why would I be able to fit two lines of 8 pt Futura in a caption box on one machine, whereas on the other machine, two lines of 8 pt Futura is too big and causes a Yield sign on the very same caption box?

Any font experts out there?