Norton Internet Security Scan Freezes, browsers crash

I cannot launch a Firefox or Internet Explorer browser session, they pop up and crash immediately.  I also noticed some of the admin permissions were swtiched off so I suspect malware. I ran the Norton Power Eraser but it did not find any issues.  If I run a Norton Internet Security Quick or Full Scan it just freezes up, but never on the same file.  Any ideas?  I tried to use Malwarebytes but it launches a web page when you first install it, so it dies with the browser ....   Help !  Thanks !