Dog has suddenly developed an attitude problem

Question
I have a Lhasa Apso that just turned 5 in February.  We've had him since he was 8 weeks and he has always had quite the personality and of course the typical "lhasatude".  Lately though he has seemed a bit grumpy and has taken to nipping at u and/or growling or shwing his teeth when we discipline him for not listening or doing things that he shouldn't be doing. We have never done anything to him physically as punishment (usually I put  him in time out in the bathroom for 5-10 mins or I take away his toys for a few hours.  Lately we haven't been letting hin sleep on the bed with us (instead we let him sleep at the foot of our bed on a bench with his blankets and if he tries to get on the bed we simply give him the "off" command)  We've never had any problems before so we are a bit confused as to why he has suddenly started with this behavior.  I did have him in obedience classes as a puppy and still practice everything we learned...Nothing has changed in our lifestyle or how we treat him...please help!

Answer
Sometimes throughout life a dog will challenge you for leadership,and he might feel that there is a weakness and try to 'move in'.Sometimes even something small can trigger it,even slightly changing a schedule. It is good that you are not letting him sleep on the bed. What will also help is to practice his training everyday for 20-40 mins a day.

It doesn't always have to be a change to trigger this type of problem,often the dog is trying to 'test' you to see what he can get away with-but keeping up his obedience will make him realize he can't get away with it