Are you using manual minify? If so, you should press "View URL" and find what's calling your fonts. It's often pre-minified stuff and W3TC destroys pre-minified stuff when it tries to optimize it.
If you are using autmatic minify, it's almost "normal" that portions of your website will have errors or will display poorly. Because automatic minify processes everything and in doing so, it includes exactly what was pre-optimized by the plug ins / theme authors and in re-optimizing pre-optimized stuff, W3TC breaks it hard.
If this is the case you should switch to manual mode and follow my tutorial on how to deal with the issue.