Help with 6 month old GSD puppy seperation anxiety?

He is the sweetest dog I have ever had, loves everybody, even complete strangers, perfectly obedient, smart, goofy, and when we're at home, quiet as could be. But when my fiance and I put him in his crate to run to the store or whatever else, he FREAKS OUT. We've been crate training since we brought him home at 10 weeks and yet he still doesn't seem to get it. We've tried excercising him till he's completely worn out and then putting him in his crate right before we leave but it doesn't matter. When we get home, he's still barking and crying like crazy. We've tried leaving the radio on, giving him a toy he's only allowed to play with when he's in the crate, leaving clothes or blankets in their with our scent, giving him a toy that dispenses treats as he plays with it...nothing. Absolutely nothing. And on top of that we can't leave him home outside of the crate or he becomes the most destructive tornado of a dog. The most he ever gets left in there is a few hours, and aside from that we're with him ALL the time. But it's like jeckyl and hyde. Perfect when we're around, psychotic when we're gone. We've even tried doggy obedience cles. It's like NOTHING is working. Yahoo answers is my last chance before I resign the poor dog to bark himself hoarse every time we go somewhere. Any ideas?