I don't remember having this problem before but I haven't animated in MED for awhile. I have a door with a key in it. I want to animate the key turning about 90 degrees. I make my first frame as a keyframe (with the key at 12:00) and then I add 4 more frames (same as the first, but not keyframes0 and then I add my last frame (a keyframe) where I turn the key to the right angle. It should interpolate from the first keyframe to the last, right? But it doessn't. The keys stays right at the 12:00 position until the last frame where it jumps to the new keyframe position. What am I doing wrong?

OK, I got it now. I didn't notice the little checkbox that says "Interpolate vertex positions". Gotta check that!

I take it back. I got it to work exactly once and now it's doing the same thing all over again, even though I am checking "Interpolate vertex positions" WTF??

Hi, make every key a key frame and animate by 45degrees value or 22 to get a track for the keyframes untill your key is at the desired pos.
Then test.

OK, I'm back on track. The trick is to make your keyframes first (your first and last frames) and then add frames in-between those frames. When you add those in-between frames, that's when you check "Interpolate vertex positions". It turns out that the "key frame" checkbox at the bottom is only for bones animation, so you just ignore it.