I may have found an issue with DOpus under Vista...
Maybe this is something weird I was doing, but when I dragged a font from a DOpus lister into an explorer windows that had C:\Windows\Fonts\ open, it would try to install the font, and then give me all these weird errors that different random bits of text (perhaps from other files, since they resembled english) were not valid font files. Like... the filename was the random text bits.
I simply used the classy and slick looking new font installer interface that Microsoft was nice enough to newly redesign for us: