Default [Q] I think I bricked my Nexus 4. Can anyone help me?

Basically, I was dicking about with the build.prop file on my Nexus 4, and now it hangs at the 'X' logo on startup. I have the original file, but I can't find any way to restore it to my phone, as the computer won't recognise it as a storage device, even in fastboot mode. Can anyone help?

thanks