Mortgage Guaranty Insurance Corp. said the higher volume of loans with high debt-to-income ratios and low FICO scores that are approved by the government-sponsored enterprises’ automated underwriting systems is partly to blame for its rising third-quarter delinquencies. The amount of delinquent loans for which the company paid for losses in the third quarter was $43.5 million, up from $21.4 million in the third quarter of 2000.