Blackberry maker Research in Motion (NSDQ: RIMM), which knows a thing or two about patent lawsuits, is headed back to court. According to filings made in the Northern District of Texas, seen by WSJ, the company is suing Motorola (NYSE: MOT) for charging excessively high fees on certain patents that it licenses out. It’s also claiming that Motorola is infringing on its own patent, including one covering a mobile device “with a keyboard optimized for use with the thumbs” (seriously). And just for good measure, Motorola has turned back around and sued RIM, again for patent infringement. To twist the knife a bit, RIM is trying to paint Motorola as a desperate company: “Having suffered losses in the marketplace, Motorola has now resorted to demanding exorbitant royalties from its competitor, RIM, for patents that Motorola claims are essential to various standards for mobile wireless telecommunications.”