Barely two months after settling a patent-infringement lawsuit that nearly shut down its U.S. service, the maker of the popular BlackBerry mobile e-mail device faces another court challenge.

Research in Motion (RIM) was sued late Friday by Visto, which alleges that the BlackBerry violates Visto patents. The federal lawsuit doesn't specify damages but seeks a court order that would effectively halt service.

Waterloo, Ontario-based RIM narrowly averted a shutdown in early March by agreeing to pay $612.5 million to end a five-year patent fight with NTP. Unlike NTP, which owns patents but doesn't make anything, Visto is an established communications-software company with 400 employees in 10 countries. Customers include Cingular Wireless, Sprint Nextel, Motorola and Nokia.

Visto has several patent lawsuits pending. Friday, it won a $3.6 million verdict against competitor Seven Networks.

"Now that we have that victory, we're more convinced of the validity of our patents," Visto co-founder Daniel Mendez said.

BlackBerry's maker conceded nothing, issuing a statement saying it "believes Visto's patents are invalid."

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