We had not thought about the time relations hp between legal malpractice and breach of fiduciary duty and how the first could become impossible while the second  could start, but the Fourth Department set it all out in Neuman v Frank ;2011 NY Slip Op 02215  ;Decided on March 25, 2011
Appellate Division, Fourth Department.  

Answering the question of whether they are duplicitive, it found that they were not, as the claims of legal malpractice applied to the time when the attorneys represented plaintiff, and a breach of fiduciary duty analysis applied to later dealings after the representation ended.
 

"Addressing defendants’ cross motion for partial summary judgment, we conclude that Supreme Court properly denied the cross motion with respect to defendant, the sole appellant. "A cause of action for legal malpractice must be based on the existence of an attorney-client relationship at the time of the alleged malpractice’ " (TVGA Eng’g, Surveying, P.C. v Gallick [appeal No. 2], 45 AD3d 1252, 1256; see Compis Servs., Inc. v Greenman, 15 AD3d 855, lv denied 4 NY3d 709). The fiduciary duty of an attorney, however, "extends both to current clients and former clients and thus is broader in scope than a cause of action for legal malpractice" (TVGA Eng’g, Surveying, P.C., 45 [*2]AD3d at 1256; see Greene v Greene, 47 NY2d 447, 453). Thus, a cause of action for legal malpractice based upon alleged misconduct occurring during the attorney’s representation of the plaintiff is not duplicative of a cause of action for breach of fiduciary duty based upon alleged misconduct occurring after the termination of the representation (see Country Club Partners, LLC v Goldman, 79 AD3d 1389, 1391; Kurman v Schnapp, 73 AD3d 435, 435-436). Although plaintiff alleged in the amended complaint that defendant’s misconduct occurred during the period from October 2004 to May 2005, when defendant represented plaintiff in transactions related to the development of a shopping center, defendant testified at his deposition that he withdrew from representing plaintiff at some point prior to April 11, 2005. Therefore, based on defendant’s own deposition testimony, defendants failed to meet their initial burden of establishing that the breach of fiduciary duty cause of action is duplicative of the legal malpractice cause of action for the period between May 2005 and the as yet unspecified date prior to April 11, 2005 when defendant ceased to represent plaintiff (see Country Club Partners, LLC, 79 AD3d at 1391; Kurman, 73 AD3d at 435-436). "