We had the same issue with out 1 1/2 Shepherd Lab X.
Tried lots of different things to curb it, Finally we contacted our local SPCA and registered for a course called Reactive Rover. The course was once a week and lasted a few weeks, once completed we had no more problems.
They offered a refresher course but we haven't needed it.
If you don't have a SPCA try googling dog obedience classes in your area.
You want to get this under control quickly, imagine if your dog injured a child.

Hope this helps.

Maddie answered on 1/11/13. Helpful? / 0