Many people are under the mistaken impression that if they are not treated well at work, or if they are gossiped about or berated by fellow employees or their boss, that as a consequence they are being subjected to a Hostile Work Environment and have a viable legal claim as a result. Actually, that is not the case.
The US Supreme Court has held that harassment and hostile environment laws were not meant to create a code of civility within the workplace. The phrase “Hostile work environment" is legal terminology, and relates to discrimination which is federally prohibited—race, color, national origin, religion, sex, age or disability. Absent proof that the hostility you complain of relates to one of the prohibited acts of discrimination, then I’m afraid that you have little solid ground to stand on with regard to legal redress.
Your issues are purely internal-political (office politics) and there is no legal remedy, I'm afraid. You should speak with your boss about the issue, but unless the boss is willing to do something, it appears that you will simply have to deal with the jealousies of an ex.
I wish you the best in 2012.
I understand that you may be disappointed by the Answer you received, as it was not particularly favorable to your situation, nor was it what I sensed you were hoping to hear. Had I been able to provide an Answer which might have given you a successful legal outcome, it would have been my pleasure to do so.