It seems like the Wildfire suffers the same fate as Desire , right now this doesn't work on Desire either , because the Desire (and probably the Wildfire too) doesn't allow writes to system once it has booted up.
I tried Typefresh to change fonts and only got errors , then i used a Fontswitcher that runs on the PC instead , it uses adb to push the fonts onto the device, and i ran it in 'desire mode' which really just mean that i have to make sure it is in recoverymode before copying the fonts.
One thing to try is to boot up recovery , pull out the build.prop and edit it , then push it back in again. Might work. (that is what the app does essentially)