Very long, sorry
MuttDog is ace. We love her to bits. She is brill with DD, well behaved, well trained. We seem to have anything sorted except bloody incessant growling. She is a Collie / Springer Cross (we think), approx 18 months old. We've had her since she was 8 weeks or so.
She is quite skitty. Cowers when she first meets someone new, but is absolutely fine within seconds. Seems to be better with women than men, quite wary of children. She's quite needy; unless we are at home she will follow DH or I wherever we go (eg when visiting MILs she follows us to the loo and scratches to come in, at home she wakes up, but stays where she is)
Biggest problem is the growling, and its driving me batty. I'm starting to get annoyed/frustrated with her, so want to sort this as soon as poss.
Any noise that she cannot see the origin of she growls. Doesn't matter what it is, kids playing, crow cawing, someone dropping something. She's even started growling if DD raises her voice (something 6 yr olds are prone to do...)
A knock at the door produces a volley of barks (I dont mind this so much)
We tried telling her off, sending her to her bed, growling back at her (from a more wooo dog friend!), I even tried the Dog Whisperer 'Dig'. I dont want to smack her though - she never has been and I'm not starting now. We've tried praising her up and giving lots of fuss, but even then she carries on growling for minutes, long after the noise has gone.
I have 3 main issues with this - one that there are quite a few kids on the street, I've never worried about the MuttDog playing out there with DD, but now she is growling I dont want the kids to be scared. Secondly that obviously she is picking up on my annoyance and has started cowering when I tell her off, I dont like this at all. Finally, MuttDog comes to work with me, but if she keeps growling/barking at visitors she'll be banned - and that means home alone most of the day 
Has anyone any tips? Anything that worked for them? Any idea why she has started doing this (prob in the last 4-5 months)? In Sep we were looking to rescue another dog, but not if MuttD is not happy.