Via TheLawyer.com:

    Sullivan claims that Charney broke his attorney-client privilege, bringing the 125-year-old firm into disrepute when he published his grievances on a website, greedyassociates.com, before officially bringing them to firm management.

    …snip….

    Sullivan is also claiming that Charney stole and leaked documents to the press.

Previous posts here, here, here and here.

ETA:

The New York Sun reports in more detail: “[Sullivan & Cromwell] also suggested that Mr. Charney stole proprietary documents from an office adjacent to his, and then leaked them to the Wall Street Journal.” (Heel click: ATL)

UPDATE:

Read the Sullivan & Cromwell v. Charney complaint here.