virtualhost woes

[eluser]TheFuzzy0ne[/eluser]
It certainly sounds like there's some external factor somewhere. I can't help thinking it's your firewall (although that wouldn't explain why it won't work on localhost). Are your other, non-CodeIgniter sites still working?

My only suggestion would be to ditch MAMP and consider looking into virtualisation. It's not ideal, but something is definitely not right, and it certainly doesn't seem like something obvious.