Subprime mortgage-related lawsuits against company executives or board members have little chance of succeeding, according to a firm that provides insurance against such claims. XL Capital Ltd. CEO Michael McGavick said yesterday that it will be tough for investors to meet the legal threshold required to extract damages. Investors filed about 100 class-action securities lawsuits in 2008 seeking to recover losses related to more than $1.7 trillion in global writedowns and other credit losses.