While it tries to resolve a dispute with Time Warner Cable over the iPad, the cable channel owner Viacom is suing another cable operator, Cablevision, over the same issue.

Viacom said Thursday it was taking the action because its discussions with Cablevision about licensing MTV, Nickelodeon and its other channels for iPad streaming have been “limited and unproductive.”

Cablevision said in a statement that its app “falls within our existing cable television licensing agreements with programmers – including Viacom.” The company continued, “It is cable television service on the iPad, which functions as a television, and is delivered securely to our customers in the home on Cablevision’s own proprietary network.”

At issue are the rights of cable operators like Time Warner Cable and Cablevision to transmit cable channels in new ways. The two companies released popular apps last spring that allowed subscribers to replicate the live-TV experience of a living room television on the iPad, effectively turning it — and conceivably other tablet computers like it — into TV screens.

Some channel owners cried foul, saying that their existing contracts with the operators did not cover new screens like the iPad. Viacom was louder than any other channel owner, and in April it sued Time Warner Cable claiming breach of contract and copyright violations. The same day, Time Warner Cable sued Viacom to seek a judge’s ruling that it has the right to stream live channels to iPads.

Conceivably, channel owners like Viacom could demand more money for the right of cable operators to stream channels over the Internet to tablet computers, creating a new revenue stream for the owners — and perhaps a new cost for consumers.

Earlier this week, amid behind-the-scenes discussions, Viacom and Time Warner Cable agreed to suspend their lawsuits temporarily. Viacom’s decision on Thursday to sue Cablevision implies that the discussions with that cable operator have been less satisfactory.

“We have taken this action to protect our valuable content,” Viacom said in a statement Thursday afternoon. “Over the last few months, we have had limited and unproductive discussions with Cablevision about licensing iPad rights. We remain open to productive discussions, but we cannot wait indefinitely while our networks are being distributed without permission.”

The company declined to comment on the discussions with Time Warner Cable.

The apps have proven to be popular among Time Warner Cable and Cablevision customers. Other cable operators are developing similar apps, but have not made them available to customers yet.