I would see what "The Dog Whisperer" has to say about this subject, I think his training techniques are great and we have used them with Sarah(my mutt) and are now doing the same with Emma. Shortly after we adopted Sarah she started growling at our kids when they would try to move her out of a chair to sit in it. Turns out it was a dominence thing. So we began dominence excersises with her (ex. banned from furniture, on walks the kids were always in front of her, and when we came in from outside she has to wait and come in last). This training ended up being a miracle for us, now (She's almost 2) she knows who is boss and is a wonderfully behaved dog who loves kids! Hope this helps, if you commit to it the problem will be solved.
http://www.cesarmillaninc.com/ This is The link to Cesar's website.
