In the latest litigation over tax shelters, two N.C. investors have filed a lawsuit accusing a Minnesota-based accounting firm and a prominent Raleigh managing director of drawing them into transactions that ran afoul of the Internal Revenue Service. In the suit filed in Wake County Superior Court, brothers John McNeill Jr. and Ronald McNeill say accounting firm RSM McGladrey Inc. and Ronald Wainwright Jr. sold them a tax strategy in 2001 designed to reduce capital gains taxes from the sale of stock they owned. They say they were told it was legal, but later discovered the IRS had been scrutinizing such strategies since 1999, according to the suit. The McNeills reached a settlement with the agency in 2004 that cost them more than $9 million in back taxes, interest and penalties, according to one of their lawyers, Charlotte attorney Gary Mauney.