Blend Shape Problem

[natj]

Hey guys...

I've got a big problem with blend shapes not tweening while animating my characters face. The blend shapes work on the key-frames themselves but when I go up one frame everything resets to zero- which makes for a very twitchy facial animation.
Ive tried animating with and without the character-set, I've tried using the 'key' and 'key all' buttons within the blend shape window, and hitting the 's' key on every key-frame.. All this the auto-key turned on, but nothing seems to work..

Please help..

Thanks

[joojaa]

What kind of setting does your keyframing curve have for infinity, andf tangent type?