I'm just starting with blender (2.36) and am experiencing a weird problem with my first character rig. I stripped it down to just the legs, now it looks as follows:
the IK chain for one leg:
- upper leg
- lower leg
- a null bone (is this what you call an 'Empty'?)
- The foot is a separate bone used as the target for an IK constraint set on the null bone

Now, this works nicely, posing both legs and all. I can also "copy current pose" and "paste flipped pose". But it screws up when I try to handle the flipped pose.

Example: I lift the left foot in pose mode. Select all bones. Copy pose, paste flipped pose. Now the right foot is up. Still in pose mode, I select the right foot, and try to move it (GKEY): The foot immediately jumps down the global z axis, stretching the leg downwards instead of lifting it up. Same happens when I insert a keyframe for the flipped pose.

Does this sound familiar to anyone? I haven't found any post hinting to a problem with this functionality, so I guess / hope I'm just doing something stupid...

Well... Try rotating, not grabing...
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1...2...3D

Well... Try rotating, not grabing and don't forget to select all the bones(if necessary ...
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1...2...3D

Turned out, I had to rotate the character around and re-align the bones (ctrl N). Now it works fine The required orientation of the armature was actually detailed quite nicely in the manual