my dog has gone mad

Question
my dog saphire is nearly 17 months of age. She used to be a lovely friendly dog but just recently when we go for a walk she growls and barks at everyone we walk past. She has also started hiding in the bathroom cupboard and sitting in the bathroom barking at the air. The last couple of weeks she has started digging the carpets almost like she is trying to dig a hole.

Answer
The first thing to do with many behavior problems is to have a good vet check.  If she hasn't been spayed or had a season for 4-6 months, it could be part of the flaky behavior that often preceeds it.  Otherwise, it may just be maturing.  

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.