Research In Motion said on Monday it is again being sued for patent infringement, less than two months after the BlackBerry maker settled a lawsuit to avert a shutdown of its U.S. service.

Visto, a wireless-messaging service company, filed on May 1 a new lawsit against Blackberry maker Research In Motion.

Visto had been also fighting in court with another wireless-messaging company, called Seven Networks. On Monday 1, Visto announced that it has won the Seven case, and filled a patent lawsit against RIM in a U.S District Court in Texas.

Visto, is one of the companies that sought to profit on the long-running patent battle between Canada's RIM and the Virginia holding company NTP. In that case, NTP asserted that its patents predated RIM's and sought an injunction that could have shut down the popular Blackberry wireless e-mail service in the U.S. Ultimately, the two companies settled, and RIM coughed up $612.5 million to make the suit go away.

RIM said in a statement that closely held Visto is alleging infringement of four patents, and is seeking an injunction and monetary damages.

RIM said it believes California-based Visto's patents are invalid and that it does not expect its customers to be impacted by Visto's complaints.

RIM said it is unlikely that any material court proceeding in the Visto case will begin before the middle of next year.