Your dog might be pacing. It's a little hard to catch if you're not used to seeing it, but try to watch when her feet hit the ground.
When a dog is doing a true walk, each foot hits the ground separately, this is called a four beat gait.
When a dog is trotting, there are two beats, with the front foot on one side and the hind foot on the
opposite side hitting the ground at the same time.
When a dog is pacing, it can look like he's doing a fast walk, but it produces a very "rolling", side to side, motion through the back. If you look carefully, you'll notice it is a two-beat gait, with the front and back foot on the
same side hitting the ground at the same time.
You will quite often see a dog pace if it is nervous or if it is tired. I hope this explanation isn't too technical for you. If you watch closely, it shouldn't be too hard to figure out if this is what you're seeing.
If this is what is going on it is a perfectly normal way of moving and absolutely nothing to worry about. It even appears in the breed standard, and is referred to as "ambling".
[This message has been edited by CarolineS (edited August 06, 1999).]