ok, it seems to me that he does not understand that he has to listen in other enviroments as well. first of all invite people over just to help you out with this, have people watching and start over, dont ask him to sit and expect him too, pretend he never knew it to begin with and reteach it all with other people in the room. once he has got this start moving to other places, such as outside a grocery store and again re-teach the basics. as for other dogs, well try a dog park? mine do it just because A) I have 5 dogs, I can put one is a stay and play fetch with the others lol and B) my dogs have been attending flyball tournys, and agility trials and other such things since they were puppys, obedience is not something I work on only at certain times, every where I take them I am working on their obedience ,, Happys stays are reinforced when I take her to the bike path and another dog comes along, I remeber one time I put her in a sit stay at the top of a hill while I went to see the other doggie, the guy I was talking to thought Happy was tied up there lol because I take my dpgs so many places with me I am always refining their skills.