A former SNR Denton client claims that the law firm dropped the ball when filing papers with the U.S. Securities and Exchange Commission and that it is therefore liable for a $7 million mortgage-backed securities deal gone awry.

Impac Secured Assets Corp. filed suit on September 20 in U.S. District Court in Los Angeles, claiming that SNR Denton dragged its feet in correcting a mistake in a 2007 SEC filing. That delay, Impac claims, led to a lawsuit filed last year by Citigroup against Impac.