I just made a walk cycle with an armature and when I simply move from the walk cycle action to another action the armature changes location. Here's the first screen capture before I switch actions.
Here's what happens when I switch actions
I should say that when I imported this armature the bone connections where messed up. In fact I couldn't find them, just sticks and circles. But I did my best to make a great looking walk cycle. Tried changing the armature location and adding new LocRotScale info to each keyframe but that didn't fix the problem.