Conseco's ( CNC) shares tumbled Friday after an analyst told shareholders they should sell the company because of ongoing credit and cash-flow problems. Investors were also spooked by the resignation of a top executive. The battering, in which Conseco's shares fell 69 cents, or 16%, to $3.56, came one day after rival GreenPoint Financial ( GPT) said it would stop making loans for manufactured homes, citing subpar returns. The decision exacerbated concerns about Conseco's own finance unit, which makes similar loans and whose top executive, Bruce Crittenden, quit Thursday. Investors bailed out en masse Friday after Salomon Smith Barney analyst Colin Devine lowered Conseco to sell from underperform and recommended it as a short sale, saying the shares "offer little, if any, value." Devine, a long-time critic of the company, said liquidation is a possibility. "Conseco continues to face myriad credit-quality challenges relating to its subprime consumer finance unit, ongoing weak operating ratios at its life insurance operations, and self-acknowledged cash-flow deficiencies at its holding company parent,'' Devine wrote. Conseco's shares have lost about 90% of their value since the company purchased the finance arm, then Green Tree Financial, in 1998. TheStreet.com has repeatedly raised questions about the company's ability to meet its debt obligations through existing cash flow; the company could face up to $1.39 billion of debt payments this year.