Dear SK,
Try to find real cause of problem. What you have mentioned happened usually when a new person becomes the cause of decrease in importance of someone who is working for long in same organization. Such type of people you will find in all type of companies. First establish yourself. Take your boss in confidence. Also that guy, let him too feel his importance. Don’t make him think that you are jeopardizing his status. Take his help whenever required. (No flattery, only when genuine). Also don’t be part of office gossips or politics unless you are in admin and want to have clue of all what is happening around. Also be like newly married person, Don’t make assumptions about colleagues on the basis of what other says. Have some experience, observe and then think what appears to you.
Remember, You can’t change others, So be flexible. If you have any interest for reading, Read 48 Laws of Power, one of the best book on office politics.
May Baba Bless You!
om sai ram!