I would still like to see him run by the vet. If it is something physical, you can't fix it without identifying it and applying the correct remedy.
Likely it is an emotional thing due to the new puppy. Find time to lavish affection and attention. Is he obedience trained? Be a good way to spend time with him if not. The key to most behavior problems is approaching things using the dog's natural instincts. Dogs see all the people and dogs in the household as a pack with each having their own rank in the pack and a top dog. Life is much easier if the 2 legged pack members outrank the 4 legged ones. You can learn to play the role of top dog by reading some books or going to a good obedience class. A good obedience class or book is about you being top dog, not about rewarding standard commands with a treat. Start at
http://www.dogsbestfriend.com/ For more on being top dog, see
http://www.dogbreedinfo.com./topdogrules.htm Top dogs have the right to bring new members into the pack. Lower ranking ones need to accept them.