What does 'a bunch of Mixed Content errors' look like? http:// and https://
The certificate for the local domain (.dev) can't be a valid cert. It's got to be self-signed. Can't register with a CA a .dev server to acquire a valid certificate. First time you accessed it via FireFox, FireFox should have complained about the certificate and you had to override/accept the cert (being self-signed and not trusted).
Do turn on debugging as Howard has suggested.
And, how is the hostname moodle.dev resolved? DNS internal to your network, or via /etc/hosts (Linux/MacOSX) or similar in Windows?
'spirit of sharing', Ken