NTP is now accusing the wireless firms of violating eight patents for e-mail services, including some that were detailed in NTP's case against RIM. In its filings, NTP asked the court for royalties based on sales of telephones, personal digital assistants and other devices capable of sending and receiving e-mail.

NTP's complaint against AT&T claims that it asserted its patents to the telecommunications giant in January 1999 and offered to license them but received "no substantive reply." Since then, AT&T has "continued to infringe the patents-in-suit, despite its knowledge of them and in reckless disregard for NTP's patent rights," NTP argues.

Hardware manufacturers whose devices are sold by AT&T have licensing deals with NTP, which "provide[s] further evidence that AT&T knowingly, recklessly and willfully infringes the patents-in-suit," NTP said. In addition to RIM, Visto, Nokia and Good Technology are licensees.

AT&T spokesman Dave Pacholczyk said the company has received the complaint but could not comment until it has been thoroughly reviewed. Rory Radding, a partner at Morrison & Foerster, simply said, "It looks like round two is beginning."

During the long-running RIM case, the BlackBerry producer filed a dozen requests for re-examination of NTP patents with the Patent and Trademark Office. In two cases, the agency rejected NTP's patent claims, but the firm appealed those decisions. The PTO's work is ongoing.

Gartner analyst Ken Dulaney said NTP is now "betting on the assumption" that those patents will be enforced. "RIM had to pay because they were in legal limbo. Those conditions no longer exist," he said. "If I were those carriers I would fight NTP."

In this instance, NTP may not be seeking as much money as they did in the BlackBerry case, so the carriers could settle, Dulaney said. "The bottom line is that NTP costs us all money, and that is not a good thing. The government needs to change the [patent] laws."

McDermott Will & Emery attorney Paul Devinsky predicted that the defendants would move for an immediate stay pending conclusion of the re-examination and that the stay would be granted.

He also suggested that NTP may be concerned that pending patent legislation on Capitol Hill would limit claims for past damages "and is seeking to be certain their damage claim is calculated under the current statute."