locknut removers are great if youve got one. ive always managed to get by using a lowcost airchisel (under 20 bucks ) and hit edge of nut couterclockwise to break free locklugs and striped lugs , are those gnx style rims like the rinkins that the lugs are in a recess hole or GM GTA's , you didnt mention if they were oe GM capped nuts , one thing i encounter alot with the oe 19 mm capped lugs is the steel cap comes off sometimes or the cap strips , pull off the cap and grab an 18mm socket or pull a cap off another lug and jam it on and try again with 19mm