There are a couple different issues I would look into that I hope help you fix it.
If you mention what font worked we could probably help out better. I would compare the font that you said worked with FontAwesome to see what the differences are. I would bet the glyphs are mapped to a different unicode area and maybe the browser doesn't read from there?
You could use a tool like Font Forge to check differences from other fonts. I noticed when trying to re-generate the FontAwesome font from Font Forge I got validation errors with the em spacing and the glyphs had errors (self-intersecting, wrong direction, missing points at extrema). I've seen this before in icon fonts and never had an issue but I haven't tested on Opera before either. If you compare trying to generate a font with something that works you could probably narrow the issue down.
Other Stuff I'm sure you covered but double checking:
I read here that having a local version of the font installed might conflict with the font embed. https://github.com/FortAwesome/Font-Awesome/issues/247
If you took the icon-font and then added your own glyphs to it then used something like font squirrel to generate all the web safe formats make sure you told the generator to add the unicode range of the glyphs you created. Once I forgot to do this and the app only added the glyphs in the a-z range. An easy way to check is to look at the gyphs tab in the demo html page and make sure all the icons are included.
You're using the proper CSS3 font-face rule and embedding eot, ttf, woff, and svg and you've waited a little bit. I noticed on some old iphones the font takes forever to display.
Using a tool like modernizr font-face feature detect might make some of the support between browsers a little easier.
I'm curious to see what the issue is.