Simple way to edit animations in Med?

Greetings, I was wondering if somebody could help me figure out a way to alter a model's animations in Med without messing the whole thing up. As it stands, if you alter one frame of a model that change is then extrapolated to all the following keys. If, in the middle of a walk cycle, I move one leg to the side, that is going to change my animation all the way through the rest of the remaining scenes. Is there a way to "lock" keyframes or something so that you can edit an individual frame without messing up all the following ones?

Click the gear icon and deselect "Use Frame Range".
This normally does the trick but can be buggy with bones animation.
What helps is to either restart MED (if you get lucky) or to press the "Auto Scene Range" icon in the lower left animation bar which then usually only messes up frames of the same scene. I just thought of this but you could try and rename every 2nd frame if you really have to, so the auto scene range only takes 1 frame long scenes into account.

Ok, thanks ...

Thanks, that auto-frame command was one of the things I was really looking for but the manual wasn't clear on. The "Use Frame Range" is being a little buggy for me, as you said it may.

One other thing now, which will be handy for changing the middle of animations, is there a way to deactivate the snap-to-grid style of movement so that I can position bones more smoothly? It would simplify tweaking models.

The gear options menu has a "Move Snap" slider.

Thanks again for your help. As you said, both options in MED are buggy and don't often work, but sometimes they do so I'll run with that ^_^.