Mac Protector is malware. That's probably why you're having problems.
You don't need any AV software as there are no viruses for Macs, so such software would be useless unless you're concerned about passing Windows viruses on to people who use Windows. But even then it can muck up your system.
That said, there is some malware that target Macs, but these are easily avoided by never installing anything you aren't sure about. Apple security patches will ONLY come via Software Update (found under the Apple menu at the top left of your menu bar).
If something is trying to scare you into thinking your Mac needs extra protection and if it didn't come from Software Update, don't download it. Things can only install on your Mac if you give it permission to by entering your password. If something is asking for your password and you don't know what it is, what it does or where it really came from, don't give it permission to install.
