Graph Editor in 2.5 extremely slow ? ( OS X )

Hi all

I restarted my evaluation of Mixamo an online pose and animation system
and noticed that in 2.5 the playback of animations is painfully slow when
the Graph Editor is open.

Mixamo exports the animations as DAE and each frame has a keyframe.

2.49 does not have that slow down.

Anybody knows why - or is this just possible bug slowdown?