Hello all... this is my first post and I hope you can help

My three year old Cocker Spaniel has just developed an attitude problem! She has always, always been wonderful with people.... too over friendly if anything (She is seriously hyper, demands attention, jumps up etc - she's over confident but always been friendly with it).
All of a sudden and completely out of the blue she has started barking aggressively at strangers who visit the house. We moved three months ago and have had a lot of strangers coming to do work to the house. She jumps up at them barking (not in a nice way) and its very embarrassing! If friends or famiy call she is her usual wonderful self, thrilled to see them and greet them.
Then last night she decided she didn't like a man we met on a walk. He was carrying a large bag and she just ran up to it barking... I could have died. We meet dozens of people when out walking and she is always pleased to see everyone. What is going on in her head!?
I started keeping her away from visitors to the house but that doesn't cure the problem... all the books advise you to get stooge people to visit but she knows all my friends and family and is very well behaved when they call. At the moment I'm keeping her on a lead and clicking and rewarding when she is calm and quiet. But I'm really concerned that this won't actually eliminate the behaviour. Things haven't improved so far and I don't get strangers calling often enough to practice! My dogs are my life and I've been gutted about this, have always brought them up using positive training techniques and socialised well. Take her to training class and she wags her bum and says hello to everyone! I must have read and surfed a million books now to find an answer, I so want to get her back to how she used to be... the other Cocker is a dream, loves everyone!! If anyone has any advice I would be sooooo grateful to hear from you

It can take 6 months or so for a dog to get used to new surroundings, so I wouldn't be ovely worried just now. Keep on doing what you are doing, but try not to get stressed out over it. She will pick up on your stress. She's had this move, which is upsetting enough, but to then have strangers coming and going will just have stressed her out more. She should calm down once things are back to normal.

Thanks very much... good to know that this could be 'normal' behaviour in the circumstances. I'll continue to do all that I can to reassure her that strangers coming in are are positive experience for her and we'll see.... Thanks for the reply though, much appreciated.

Once she starts barking  I would put her behind maybe a baby gate, and ignore her, no eye contact,when she is quiet can you have a pot of really tasty treats to hand so when a stranger to her has come in, (and yes, get stooges if you can ) they can greet her with a positive treat, once she is calm. The large bag with the stranger sounds like she is not a confident little soul at all and maybe going through a 'fear stage' which has been enhanced, maybe, by moving, although dogs are pretty adaptable. Look at dogs that live with the homeless? They are calm and take everything in their stride, bless them.

How old is she? And you are also winding yourself up, quite understandably. Maybe be more confident and upright in your manner. Kind, but assertivel, not reassuring her with petting or by saying 'be good girl' (cos all she will hear is the 'good girl' when she starts or goes potty at the door, as this can be misconstrude by her as praising the behaviour. Also just walk confidently on when she sees something she is afraid of. Tighten the lead and talking will give her signals to react to your worry. Walk on confidently with a 'No problem' attitude. She should learn from you that there really is no problem as her leader is not at all worried.

Hope that helps a little. Let us know how you get on.  

Golden Lady has made a very good point about you winding yourself up. If she is picking up on your anxiety
this is going to make her worse. Dogs are very finely tuned to pick up on other pack members feelings and if you are sending out 'worried' signals she will pick them up and think there is danger present.