My city beagle has separation anxiety...

My sister and I adopted a 3-year-old beagle from the SPCA back home in Buffalo and brought him to New York City with us. At first, Charlie didn't act out, so we let him hang around the apartment when we were gone. However, he started to mess (both varieties) in the house while were gone, often when alone for only a few hours and even when we stepped out to the grocery store, thus leading us to believe it was out of frustration. We began to crate train him, but when left alone in the crate, he would scratch up his snout trying to get out. We then tried confining him to the bathroom, but he proved capable of scaling a 4-foot gate -- the daily puppy-proofing was also very laborious, as he would destroy anything he could get his teeth on (including the shower curtain). We have gone back to the crate (with all rough edges padded over), and while he isn't scratching himself up anymore, he's taken to panting heavily and crying once put in and barking as soon as he hears the apartment door close. He has a Kong ball and other alone-safe toys, but it doesn't seem to make a difference. He also usually visits the dog park twice before being crated in the afternoon, so I can't imagine it's lack of stimulation. We're very afraid the neighbors will start to complain and we'll be forced to give up Charlie, who is otherwise great with kids, wonderful with other dogs, and very mellow when someone is home. Any suggestions on easing Charlie's separation anxiety. [align=right]