Keyframe starts at frame 48

[Mastin1]

Hi!
I have a bone layer about an head. It's full of layer regarding eyes, shadows, nose, hairs, mouth, lips etc. For each part I basically created smart bones in order to give to it a fluent movement. Usually my smart bones are created from frame 0 to frame 24.
Dunno why but when I try to animate it on timeline, automatically the keyframe of the bones starts at the frame 48 and I can't move them in the previous frames.

It wouldn't be a big problem if when I need to modify some smart bone or the layer position in the frame 0 I can't because nothing is moving at all.
What could be the problem?

[synthsin75]

Check the sequencer.