NAV 2012 stopped working/won't reinstall

Had a bluescreen fail overnight, traced to AV2012.  I've used the removal tool (several times), and reinstalled NAV (several times).  Each time I get a "successful" message, but 1) no tray icon, 2) nothing runs/no disk activity 3) "free upgrade" says no product installed.

I've spent all evening titting around with this and am getting seriously pissed off.  I'm reluctant to go to AVG or McAfee as they're so processor hungry - but I can't (daren't) use my laptop & its affecting my business.  HELP!!