I had this problem too last night.

I didn't have auto-loot on, and was shift-clicking to get loot. I think I was moving forward a bit on my main toon while I finished looting and this made my 2 alts start running crazy, though my main did not move. I switched to auto-loot and haven't had the problem since.

But when this did happen, I had to do what the above posters have been saying, click to the alternate window and type "W". Hopefully if you do this fast enough, your "follow" macro will bring them back in line with out manually guiding them.