Font issues between Macs and PCs

Hi, I work in a company that uses GIS software for mapping, and we are using Unicode fonts (Myriad and Minion) on our maps, Problem is, map labels come in as multiple segments (eg John St), and when we convert to a single text string or move the text along a curved road, the label spreads out. This only occurs with Unicode, not with Arial or Obelix. The font guru who works with these fonts uses a Mac, while here we use PCs. We had a crack at regenerating the same fonts in Fontlab 5 and that fixed the problem. When this font guru did the same thing and sent it back the problem was still there. I was just wondering if this is because he is using a Mac or could it be some other problem. We are both using Fontlab 5. I know GIS would be something unfamilliar to all or most of you but I was just wondering if a similar problem could be happening with any other software packages or if you are familliar with the problem. We could simply regenerate the font here but other departments/printers use Unicode and that could potentially cause problems their end.

Thanks

Josh