In comparison to the prior article, you need not put the insurer on notice until and unless you reasonably know that there really is a claim against the attorney.  In another short subscription blurb:

"MADISON, Wis. – An insurer owes a duty to defend and indemnify its insured against claims of malpractice because the insured attorney did not have a basis to believe that his acts might reasonably be expected to be the basis of a legal malpractice claim against him before the inception of the insurance policy, a federal judge said June 13 (Continental Casualty Co. v. William A. Schembera, Schembera & Smith and Evan Zimmerman, NO. 07-048, W.D. Wisc.; 2007 U.S. Dist. LEXIS 43302). Full story on lexis.com "