IK-FK switch works with object but no with bone

I was trying to make an IK-FK switch, and I’ve found a problem. I have an FK chain, an IK chain and a deform chain. The bones in the deform chain are constrained to the bones in the FK and IK chains.
If I use another object to drive the IPO curves for the influence, the switch runs OK. But if instead of the object driver I use another bone of the same armature, nothing happens.
Any idea about what I can be doing wrong?

You can see a simplified blend with the problem in (http://www.pairal.net/notWorking.blend). Just three bones (bone 3 has copy rotation to bones 1 and 2) and the controller bone (x). If instead of x I use the cube, it works OK.

Thanks in advance for your help!

I can’t seem to download your file for some reason …

But perhaps you are not selecting Pose for your driver bones (the default is object) …

Edit : I think this might be a bug … The driver when it is a bone will not interactively update in the viewport … you have to change the frame you are in manually then it will update in the 3D view …

Here’s my simple example made the “bugfix” 2.47 …

Attachments

IK_driver bug.blend (147 KB)

In order to try to find if this is a bug or if I have something wrong, I’ve updated the blend with a clearer example (http://www.pairal.net/notWorking.blend).
There are two equal armatures with two bones each: a base bone and a target bone. The base bone has a copy rotation constraint to the target bone, that is posed with a 90º rotation. Base bone has an initial influence of 0.
In the upper armature, the constraint is driven by a third bone (the driver). In the lower armature it is driven by an object (a cube). Both IPOs are equal.
If you rotate the cube, the lower armature rotates accordingly, but if you rotate the driver bone in the upper armature, the base bone doesn’t respond.
Am I making something wrong? Is it a bug? In this case, is there any workaround?
I’m using the official 2.47 release.

to Vertex Pusher: I’ve tried to change manually the frame, but in my case I haven’t obtained any change.

Just after having written the last post, I’ve found that Vertex pusher were right. If, after, moving the driver bone, I change the frame, the base bone moves correctly.
I hadn’t seen it because I moved the green line in the ipo curve, and I had to use the box with the number of the frame.
So as he said this must be a bug.