I have also had troubles getting the Myriad Roman font to work on my Mac (10.1.5).
I put the font into any of the Fonts folders and load up Textedit. The font is never displayed in the list and instead there is a name called --font8349--. In Appleworks, the font names are all displayed correctly, however when used the text comes out totally in pixcells.
I have sent the font I have to a few people who have Jaguar installed and they all verify that it works as it should, so it may just be a problem with pre-jaguar OS X.
I would be eternally grateful if perhaps a couple of people who are on either pre-10.2 or 10.2 could see if they can get the font to work correctly.
Thank you.