Problem with the chat window

Hello,When I move the chat window in SB to a new position or immediately after sending a message in FS2002, the engines drop RPM and the aircraft speed decreases by about 50 knots. Fortunately, the RPM and speed increases again to their original values in about a minute. This is more of an annoyance than a serious problem but I am puzzled as to why this occurs. It does this also when I change things in Flight Navigator. Has anyone experienced this strange behaviour in SB or FS Nav?Maurice