By Joris Evers, IDG News Service

Yahoo may be taking a hint from Microsoft: Pending changes to its instant messaging service will probably lock out users of third-party IM clients.

Yahoo has started notifying users of older versions of its Yahoo Messenger client that they must upgrade by September 24 or be unable to log on, says Mary Osako, a Yahoo spokesperson.

However, the change does not affect only Yahoo users. As a result of the update, third-party IM clients could also be locked out of the Yahoo IM network. Users who connect to Yahoo's network via some versions of Trillian, a popular IM client that consolidates multiple IM accounts, also are getting Yahoo's upgrade alert each time they log on.

"The upgrade likely will affect third-party clients," Osako confirms. Cerulean Studios, maker of the Trillian IM client, did not respond to a request for comment.

More on this article can be found here: PCWorld.