Hmmm...a similar thing has happened with Lady. She's never been necessarily *good* about nails, but the past 3 times.......for no apparent reason.....she has been AWFUL. She's the sweetest dog in the world about everything else. I've had to muzzle her, she almost gets insane now if you even *touch* her feet.

You definitely need to help with this before it gets worse....

I'd start over again, like he's a puppy. Gently pick up a paw and just use the clippers near it. If he acts calm, give him a treat and praise. I'd pratice this frequently, and also play with his feet.

He's still growing up, and it may just be a phase, but I think contacting a trainer is a good idea.