Research in Motion is in court again. This time RIM has filed suit to prevent Xerox from demanding patent royalties, according to court documents. RIM, which is already in patent litigation with NTP and Good Technology, said it filed its suit against Xerox on July 17 in a federal court in Hartford, Conn., as a defensive move. News.com reports that Xerox claims that RIM has infringed on some of its patents, and RIM said Xerox has been threatening a lawsuit since August 2002.