Different treatment because you complained is what you are allegedly encountering. That's illegal retaliation. File a follow-up complaint and give specific details regarding who won't talk to you, specific dates and times this has happened, etc. Your HR rep didn't do a full job the first go-round in explaining at the conclusion of the investigation what the expectations were: no retaliation. He or she should have ideally given you both a copy of the Company policy in addition to verbally reviewing expectations. Tell HR that you're facing a department of pervasive hostility aimed squarely at you because of your complaint, engineered by your supervisor.